SQL

 

SQL Tutorial

SQL tutorial provides basic and advanced concepts of SQL. Our SQL tutorial is designed for both beginners and professionals.

SQL (Structured Query Language) is used to perform operations on the records stored in the database, such as updating records, inserting records, deleting records, creating and modifying database tables, views, etc.

SQL is not a database system, but it is a query language.

Suppose you want to perform the queries of SQL language on the stored data in the database. You are required to install any database management system in your systems, for example, Oracle, MySQL, MongoDB, PostgreSQL, SQL Server, DB2, etc.

What is SQL?

SQL is a short-form of the structured query language, and it is pronounced as S-Q-L or sometimes as See-Quell.

This database language is mainly designed for maintaining the data in relational database management systems. It is a special tool used by data professionals for handling structured data (data which is stored in the form of tables). It is also designed for stream processing in RDSMS.

You can easily create and manipulate the database, access and modify the table rows and columns, etc. This query language became the standard of ANSI in the year of 1986 and ISO in the year of 1987.

If you want to get a job in the field of data science, then it is the most important query language to learn. Big enterprises like Facebook, Instagram, and LinkedIn, use SQL for storing the data in the back-end.

Why SQL?

Nowadays, SQL is widely used in data science and analytics. Following are the reasons which explain why it is widely used:

• The basic use of SQL for data professionals and SQL users is to insert, update, and delete the data from the relational database.
• SQL allows the data professionals and users to retrieve the data from the relational database management systems.
• It also helps them to describe the structured data.
• It allows SQL users to create, drop, and manipulate the database and its tables.
• It also helps in creating the view, stored procedure, and functions in the relational database.
• It allows you to define the data and modify that stored data in the relational database.
• It also allows SQL users to set the permissions or constraints on table columns, views, and stored procedures.

History of SQL

"A Relational Model of Data for Large Shared Data Banks" was a paper which was published by the great computer scientist "E.F. Codd" in 1970.

The IBM researchers Raymond Boyce and Donald Chamberlin originally developed the SEQUEL (Structured English Query Language) after learning from the paper given by E.F. Codd. They both developed the SQL at the San Jose Research laboratory of IBM Corporation in 1970.

At the end of the 1970s, relational software Inc. developed their own first SQL using the concepts of E.F. Codd, Raymond Boyce, and Donald Chamberlin. This SQL was totally based on RDBMS. Relational Software Inc., which is now known as Oracle Corporation, introduced the Oracle V2 in June 1979, which is the first implementation of SQL language. This Oracle V2 version operates on VAX computers.

Process of SQL

When we are executing the command of SQL on any Relational database management system, then the system automatically finds the best routine to carry out our request, and the SQL engine determines how to interpret that particular command.

Structured Query Language contains the following four components in its process:

• Query Dispatcher
• Optimization Engines
• Classic Query Engine
• SQL Query Engine, etc.

A classic query engine allows data professionals and users to maintain non-SQL queries. The architecture of SQL is shown in the following diagram:

Some SQL Commands

The SQL commands help in creating and managing the database. The most common SQL commands which are highly used are mentioned below:

1. CREATE command
2. UPDATE command
3. DELETE command
4. SELECT command
5. DROP command
6. INSERT command

CREATE Command

This command helps in creating the new database, new table, table view, and other objects of the database.

UPDATE Command

This command helps in updating or changing the stored data in the database.

DELETE Command

This command helps in removing or erasing the saved records from the database tables. It erases single or multiple tuples from the tables of the database.

SELECT Command

This command helps in accessing the single or multiple rows from one or multiple tables of the database. We can also use this command with the WHERE clause.

DROP Command

This command helps in deleting the entire table, table view, and other objects from the database.

INSERT Command

This command helps in inserting the data or records into the database tables. We can easily insert the records in single as well as multiple rows of the table.

SQL vs No-SQL

The following table describes the differences between the SQL and NoSQL, which are necessary to understand:

SQL	No-SQL
1. SQL is a relational database management system.	1. While No-SQL is a non-relational or distributed database management system.
2. The query language used in this database system is a structured query language.	2. The query language used in the No-SQL database systems is a non-declarative query language.
3. The schema of SQL databases is predefined, fixed, and static.	3. The schema of No-SQL databases is a dynamic schema for unstructured data.
4. These databases are vertically scalable.	4. These databases are horizontally scalable.
5. The database type of SQL is in the form of tables, i.e., in the form of rows and columns.	5. The database type of No-SQL is in the form of documents, key-value, and graphs.
6. It follows the ACID model.	6. It follows the BASE model.
7. Complex queries are easily managed in the SQL database.	7. NoSQL databases cannot handle complex queries.
8. This database is not the best choice for storing hierarchical data.	8. While No-SQL database is a perfect option for storing hierarchical data.
9. All SQL databases require object-relational mapping.	9. Many No-SQL databases do not require object-relational mapping.
10. Gauges, CircleCI, Hootsuite, etc., are the top enterprises that are using this query language.	10. Airbnb, Uber, and Kickstarter are the top enterprises that are using this query language.
11. SQLite, Ms-SQL, Oracle, PostgreSQL, and MySQL are examples of SQL database systems.	11. Redis, MongoDB, Hbase, BigTable, CouchDB, and Cassandra are examples of NoSQL database systems.

Advantages of SQL

SQL provides various advantages which make it more popular in the field of data science. It is a perfect query language which allows data professionals and users to communicate with the database. Following are the best advantages or benefits of Structured Query Language:

1. No programming needed

SQL does not require a large number of coding lines for managing the database systems. We can easily access and maintain the database by using simple SQL syntactical rules. These simple rules make the SQL user-friendly.

2. High-Speed Query Processing

A large amount of data is accessed quickly and efficiently from the database by using SQL queries. Insertion, deletion, and updation operations on data are also performed in less time.

3. Standardized Language

SQL follows the long-established standards of ISO and ANSI, which offer a uniform platform across the globe to all its users.

4. Portability

The structured query language can be easily used in desktop computers, laptops, tablets, and even smartphones. It can also be used with other applications according to the user's requirements.

5. Interactive language

We can easily learn and understand the SQL language. We can also use this language for communicating with the database because it is a simple query language. This language is also used for receiving the answers to complex queries in a few seconds.

6. More than one Data View

The SQL language also helps in making the multiple views of the database structure for the different database users.

Disadvantages of SQL

With the advantages of SQL, it also has some disadvantages, which are as follows:

1. Cost

The operation cost of some SQL versions is high. That's why some programmers cannot use the Structured Query Language.

2. Interface is Complex

Another big disadvantage is that the interface of Structured query language is difficult, which makes it difficult for SQL users to use and manage it.

3. Partial Database control

The business rules are hidden. So, the data professionals and users who are using this query language cannot have full database control.

SQL Syntax

When you want to do some operations on the data in the database, then you must have to write the query in the predefined syntax of SQL.

The syntax of the structured query language is a unique set of rules and guidelines, which is not case-sensitive. Its Syntax is defined and maintained by the ISO and ANSI standards.

Following are some most important points about the SQL syntax which are to remember:

• You can write the keywords of SQL in both uppercase and lowercase, but writing the SQL keywords in uppercase improves the readability of the SQL query.
• SQL statements or syntax are dependent on text lines. We can place a single SQL statement on one or multiple text lines.
• You can perform most of the action in a database with SQL statements.
• SQL syntax depends on relational algebra and tuple relational calculus.

SQL Statement

SQL statements tell the database what operation you want to perform on the structured data and what information you would like to access from the database.

The statements of SQL are very simple and easy to use and understand. They are like plain English but with a particular syntax.

Simple Example of SQL statement:

1. SELECT "column_name" FROM "table_name";    

Each SQL statement begins with any of the SQL keywords and ends with the semicolon (;). The semicolon is used in the SQL for separating the multiple Sql statements which are going to execute in the same call. In this SQL tutorial, we will use the semicolon (;) at the end of each SQL query or statement.

Most Important SQL Commands and Statements

1. Select Statement
2. Update Statement
3. Delete Statement
4. Create Table Statement
5. Alter Table Statement
6. Drop Table Statement
7. Create Database Statement
8. Drop Database Statement
9. Insert Into Statement
10. Truncate Table Statement
11. Describe Statement
12. Distinct Clause
13. Commit Statement
14. Rollback Statement
15. Create Index Statement
16. Drop Index Statement
17. Use Statement

Let's discuss each statement in short one by one with syntax and one example:

1. SELECT Statement

This SQL statement reads the data from the SQL database and shows it as the output to the database user.

Syntax of SELECT Statement:

1. SELECT column_name1, column_name2, .…, column_nameN  
2.     [ FROM table_name ]  
3.     [ WHERE condition ]  
4.     [ ORDER BY order_column_name1 [ ASC | DESC ], .... ];  

Example of SELECT Statement:

1. SELECT Emp_ID, First_Name, Last_Name, Salary, City  
2. FROM Employee_details  
3. WHERE Salary = 100000  
4. ORDER BY Last_Name  

This example shows the Emp_ID, First_Name, Last_Name, Salary, and City of those employees from the Employee_details table whose Salary is 100000. The output shows all the specified details according to the ascending alphabetical order of Last_Name.

3. UPDATE Statement

This SQL statement changes or modifies the stored data in the SQL database.

Syntax of UPDATE Statement:

1. UPDATE table_name  
2. SET column_name1 = new_value_1, column_name2 = new_value_2, ...., column_nameN = new_value_N  
3. [ WHERE  CONDITION ];  

Example of UPDATE Statement:

1. UPDATE Employee_details  
2. SET Salary = 100000  
3. WHERE Emp_ID = 10;  

This example changes the Salary of those employees of the Employee_details table whose Emp_ID is 10 in the table.

3. DELETE Statement

This SQL statement deletes the stored data from the SQL database.

Syntax of DELETE Statement:

1. DELETE FROM table_name  
2. [ WHERE CONDITION ];  

Example of DELETE Statement:

1. DELETE FROM Employee_details  
2. WHERE First_Name = 'Sumit';  

This example deletes the record of those employees from the Employee_details table whose First_Name is Sumit in the table.

4. CREATE TABLE Statement

This SQL statement creates the new table in the SQL database.

Syntax of CREATE TABLE Statement:

1. CREATE TABLE table_name  
2. (  
3. column_name1 data_type [column1 constraint(s)],  
4. column_name2 data_type [column2 constraint(s)],  
5. .....  
6. .....,  
7. column_nameN data_type [columnN constraint(s)],  
8. PRIMARY KEY(one or more col)  
9. );  

Example of CREATE TABLE Statement:

1. CREATE TABLE Employee_details(  
2.       Emp_Id NUMBER(4) NOT NULL,  
3.       First_name VARCHAR(30),  
4.       Last_name VARCHAR(30),  
5.       Salary Money,  
6.       City VARCHAR(30),  
7.       PRIMARY KEY (Emp_Id)  
8. );  

This example creates the table Employee_details with five columns or fields in the SQL database. The fields in the table are Emp_Id, First_Name, Last_Name, Salary, and City. The Emp_Id column in the table acts as a primary key, which means that the Emp_Id column cannot contain duplicate values and null values.

5. ALTER TABLE Statement

This SQL statement adds, deletes, and modifies the columns of the table in the SQL database.

Syntax of ALTER TABLE Statement:

1. ALTER TABLE table_name ADD column_name datatype[(size)];  

The above SQL alter statement adds the column with its datatype in the existing database table.

1. ALTER TABLE table_name MODIFY column_name column_datatype[(size)];  

The above 'SQL alter statement' renames the old column name to the new column name of the existing database table.

1. ALTER TABLE table_name DROP COLUMN column_name;  

The above SQL alter statement deletes the column of the existing database table.

Example of ALTER TABLE Statement:

1. ALTER TABLE Employee_details   
2. ADD Designation VARCHAR(18);  

This example adds the new field whose name is Designation with size 18 in the Employee_details table of the SQL database.

6. DROP TABLE Statement

This SQL statement deletes or removes the table and the structure, views, permissions, and triggers associated with that table.

Syntax of DROP TABLE Statement:

1. DROP TABLE [ IF EXISTS ]  
2. table_name1, table_name2, ……, table_nameN;  

The above syntax of the drop statement deletes specified tables completely if they exist in the database.

Example of DROP TABLE Statement:

1. DROP TABLE Employee_details;   

This example drops the Employee_details table if it exists in the SQL database. This removes the complete information if available in the table.

7. CREATE DATABASE Statement

This SQL statement creates the new database in the database management system.

Syntax of CREATE DATABASE Statement:

1. CREATE DATABASE database_name;  

Example of CREATE DATABASE Statement:

1. CREATE DATABASE Company;   

The above example creates the company database in the system.

8. DROP DATABASE Statement

This SQL statement deletes the existing database with all the data tables and views from the database management system.

Syntax of DROP DATABASE Statement:

1. DROP DATABASE database_name;  

Example of DROP DATABASE Statement:

1. DROP DATABASE Company;   

The above example deletes the company database from the system.

9. INSERT INTO Statement

This SQL statement inserts the data or records in the existing table of the SQL database. This statement can easily insert single and multiple records in a single query statement.

Syntax of insert a single record:

1. INSERT INTO table_name  
2. (   
3. column_name1,   
4. column_name2, .…,   
5. column_nameN  
6. )  
7. VALUES   
8. (value_1,   
9. value_2, ..…,   
10. value_N  
11. );  

Example of insert a single record:

1. INSERT INTO Employee_details  
2. (   
3. Emp_ID,   
4. First_name,  
5. Last_name,  
6. Salary,  
7. City  
8. )  
9. VALUES   
10. (101,   
11. Akhil,  
12. Sharma,  
13. 40000,  
14. Bangalore  
15. );  

This example inserts 101 in the first column, Akhil in the second column, Sharma in the third column, 40000 in the fourth column, and Bangalore in the last column of the table Employee_details.

Syntax of inserting a multiple records in a single query:

1. INSERT INTO table_name  
2. ( column_name1, column_name2, .…, column_nameN)  
3. VALUES (value_1, value_2, ..…, value_N), (value_1, value_2, ..…, value_N),….;  

Example of inserting multiple records in a single query:

1. INSERT INTO Employee_details  
2. ( Emp_ID, First_name, Last_name, Salary, City )  
3. VALUES (101, Amit, Gupta, 50000, Mumbai), (101,  John, Aggarwal, 45000, Calcutta), (101, Sidhu, Arora, 55000, Mumbai);  

This example inserts the records of three employees in the Employee_details table in the single query statement.

10. TRUNCATE TABLE Statement

This SQL statement deletes all the stored records from the table of the SQL database.

Syntax of TRUNCATE TABLE Statement:

1. TRUNCATE TABLE table_name;  

Example of TRUNCATE TABLE Statement:

1. TRUNCATE TABLE Employee_details;  

This example deletes the record of all employees from the Employee_details table of the database.

11. DESCRIBE Statement

This SQL statement tells something about the specified table or view in the query.

Syntax of DESCRIBE Statement:

1. DESCRIBE table_name | view_name;  

Example of DESCRIBE Statement:

1. DESCRIBE Employee_details;  

This example explains the structure and other details about the Employee_details table.

12. DISTINCT Clause

This SQL statement shows the distinct values from the specified columns of the database table. This statement is used with the SELECT keyword.

Syntax of DISTINCT Clause:

1. SELECT DISTINCT column_name1, column_name2, ...  
2. FROM table_name;  

Example of DISTINCT Clause:

1. SELECT DISTINCT City, Salary  
2. FROM Employee_details;  

This example shows the distinct values of the City and Salary column from the Employee_details table.

13. COMMIT Statement

This SQL statement saves the changes permanently, which are done in the transaction of the SQL database.

Syntax of COMMIT Statement:

1. COMMIT  

Example of COMMIT Statement:

1. DELETE FROM Employee_details  
2. WHERE salary = 30000;  
3. COMMIT;  

This example deletes the records of those employees whose Salary is 30000 and then saves the changes permanently in the database.

14. ROLLBACK Statement

This SQL statement undo the transactions and operations which are not yet saved to the SQL database.

Syntax of ROLLBACK Statement:

1. ROLLBACK  

Example of ROLLBACK Statement:

1. DELETE FROM Employee_details  
2. WHERE City = Mumbai;  
3. ROLLBACK;  

This example deletes the records of those employees whose City is Mumbai and then undo the changes in the database.

15. CREATE INDEX Statement

This SQL statement creates the new index in the SQL database table.

Syntax of CREATE INDEX Statement:

1. CREATE INDEX index_name  
2. ON table_name ( column_name1, column_name2, …, column_nameN );  

Example of CREATE INDEX Statement:

1. CREATE INDEX idx_First_Name  
2. ON employee_details (First_Name);  

This example creates an index idx_First_Name on the First_Name column of the Employee_details table.

16. DROP INDEX Statement

This SQL statement deletes the existing index of the SQL database table.

Syntax of DROP INDEX Statement:

1. DROP INDEX index_name;   

Example of DROP INDEX Statement:

1. DROP INDEX idx_First_Name;   

This example deletes the index idx_First_Name from the SQL database.

17. USE Statement

This SQL statement selects the existing SQL database. Before performing the operations on the database table, you have to select the database from the multiple existing databases.

Syntax of USE Statement:

1. USE database_name;  

Example of USE DATABASE Statement:

1. USE Company;   

This example uses the company database.

SQL Data Types

Data types are used to represent the nature of the data that can be stored in the database table. For example, in a particular column of a table, if we want to store a string type of data then we will have to declare a string data type of this column.

Data types mainly classified into three categories for every database.

• String Data types
• Numeric Data types
• Date and time Data types

Data Types in MySQL, SQL Server and Oracle Databases

MySQL Data Types

A list of data types used in MySQL database. This is based on MySQL 8.0.

MySQL String Data Types

CHAR(Size)	It is used to specify a fixed length string that can contain numbers, letters, and special characters. Its size can be 0 to 255 characters. Default is 1.
VARCHAR(Size)	It is used to specify a variable length string that can contain numbers, letters, and special characters. Its size can be from 0 to 65535 characters.
BINARY(Size)	It is equal to CHAR() but stores binary byte strings. Its size parameter specifies the column length in the bytes. Default is 1.
VARBINARY(Size)	It is equal to VARCHAR() but stores binary byte strings. Its size parameter specifies the maximum column length in bytes.
TEXT(Size)	It holds a string that can contain a maximum length of 255 characters.
TINYTEXT	It holds a string with a maximum length of 255 characters.
MEDIUMTEXT	It holds a string with a maximum length of 16,777,215.
LONGTEXT	It holds a string with a maximum length of 4,294,967,295 characters.
ENUM(val1, val2, val3,...)	It is used when a string object having only one value, chosen from a list of possible values. It contains 65535 values in an ENUM list. If you insert a value that is not in the list, a blank value will be inserted.
SET( val1,val2,val3,....)	It is used to specify a string that can have 0 or more values, chosen from a list of possible values. You can list up to 64 values at one time in a SET list.
BLOB(size)	It is used for BLOBs (Binary Large Objects). It can hold up to 65,535 bytes.

MySQL Numeric Data Types

BIT(Size)	It is used for a bit-value type. The number of bits per value is specified in size. Its size can be 1 to 64. The default value is 1.
INT(size)	It is used for the integer value. Its signed range varies from -2147483648 to 2147483647 and unsigned range varies from 0 to 4294967295. The size parameter specifies the max display width that is 255.
INTEGER(size)	It is equal to INT(size).
FLOAT(size, d)	It is used to specify a floating point number. Its size parameter specifies the total number of digits. The number of digits after the decimal point is specified by d parameter.
FLOAT(p)	It is used to specify a floating point number. MySQL used p parameter to determine whether to use FLOAT or DOUBLE. If p is between 0 to24, the data type becomes FLOAT (). If p is from 25 to 53, the data type becomes DOUBLE().
DOUBLE(size, d)	It is a normal size floating point number. Its size parameter specifies the total number of digits. The number of digits after the decimal is specified by d parameter.
DECIMAL(size, d)	It is used to specify a fixed point number. Its size parameter specifies the total number of digits. The number of digits after the decimal parameter is specified by d parameter. The maximum value for the size is 65, and the default value is 10. The maximum value for d is 30, and the default value is 0.
DEC(size, d)	It is equal to DECIMAL(size, d).
BOOL	It is used to specify Boolean values true and false. Zero is considered as false, and nonzero values are considered as true.

MySQL Date and Time Data Types

DATE	It is used to specify date format YYYY-MM-DD. Its supported range is from '1000-01-01' to '9999-12-31'.
DATETIME(fsp)	It is used to specify date and time combination. Its format is YYYY-MM-DD hh:mm:ss. Its supported range is from '1000-01-01 00:00:00' to 9999-12-31 23:59:59'.
TIMESTAMP(fsp)	It is used to specify the timestamp. Its value is stored as the number of seconds since the Unix epoch('1970-01-01 00:00:00' UTC). Its format is YYYY-MM-DD hh:mm:ss. Its supported range is from '1970-01-01 00:00:01' UTC to '2038-01-09 03:14:07' UTC.
TIME(fsp)	It is used to specify the time format. Its format is hh:mm:ss. Its supported range is from '-838:59:59' to '838:59:59'
YEAR	It is used to specify a year in four-digit format. Values allowed in four digit format from 1901 to 2155, and 0000.

SQL Server Data Types

SQL Server String Data Type

char(n)	It is a fixed width character string data type. Its size can be up to 8000 characters.
varchar(n)	It is a variable width character string data type. Its size can be up to 8000 characters.
varchar(max)	It is a variable width character string data types. Its size can be up to 1,073,741,824 characters.
text	It is a variable width character string data type. Its size can be up to 2GB of text data.
nchar	It is a fixed width Unicode string data type. Its size can be up to 4000 characters.
nvarchar	It is a variable width Unicode string data type. Its size can be up to 4000 characters.
ntext	It is a variable width Unicode string data type. Its size can be up to 2GB of text data.
binary(n)	It is a fixed width Binary string data type. Its size can be up to 8000 bytes.
varbinary	It is a variable width Binary string data type. Its size can be up to 8000 bytes.
image	It is also a variable width Binary string data type. Its size can be up to 2GB.

SQL Server Numeric Data Types

bit	It is an integer that can be 0, 1 or null.
tinyint	It allows whole numbers from 0 to 255.
Smallint	It allows whole numbers between -32,768 and 32,767.
Int	It allows whole numbers between -2,147,483,648 and 2,147,483,647.
bigint	It allows whole numbers between -9,223,372,036,854,775,808 and 9,223,372,036,854,775,807.
float(n)	It is used to specify floating precision number data from -1.79E+308 to 1.79E+308. The n parameter indicates whether the field should hold the 4 or 8 bytes. Default value of n is 53.
real	It is a floating precision number data from -3.40E+38 to 3.40E+38.
money	It is used to specify monetary data from -922,337,233,685,477.5808 to 922,337,203,685,477.5807.

SQL Server Date and Time Data Type

datetime	It is used to specify date and time combination. It supports range from January 1, 1753, to December 31, 9999 with an accuracy of 3.33 milliseconds.
datetime2	It is used to specify date and time combination. It supports range from January 1, 0001 to December 31, 9999 with an accuracy of 100 nanoseconds
date	It is used to store date only. It supports range from January 1, 0001 to December 31, 9999
time	It stores time only to an accuracy of 100 nanoseconds
timestamp	It stores a unique number when a new row gets created or modified. The time stamp value is based upon an internal clock and does not correspond to real time. Each table may contain only one-time stamp variable.

SQL Server Other Data Types

Sql_variant	It is used for various data types except for text, timestamp, and ntext. It stores up to 8000 bytes of data.
XML	It stores XML formatted data. Maximum 2GB.
cursor	It stores a reference to a cursor used for database operations.
table	It stores result set for later processing.
uniqueidentifier	It stores GUID (Globally unique identifier).

Oracle Data Types

Oracle String data types

CHAR(size)	It is used to store character data within the predefined length. It can be stored up to 2000 bytes.
NCHAR(size)	It is used to store national character data within the predefined length. It can be stored up to 2000 bytes.
VARCHAR2(size)	It is used to store variable string data within the predefined length. It can be stored up to 4000 byte.
VARCHAR(SIZE)	It is the same as VARCHAR2(size). You can also use VARCHAR(size), but it is suggested to use VARCHAR2(size)
NVARCHAR2(size)	It is used to store Unicode string data within the predefined length. We have to must specify the size of NVARCHAR2 data type. It can be stored up to 4000 bytes.

Oracle Numeric Data Types

NUMBER(p, s)	It contains precision p and scale s. The precision p can range from 1 to 38, and the scale s can range from -84 to 127.
FLOAT(p)	It is a subtype of the NUMBER data type. The precision p can range from 1 to 126.
BINARY_FLOAT	It is used for binary precision( 32-bit). It requires 5 bytes, including length byte.
BINARY_DOUBLE	It is used for double binary precision (64-bit). It requires 9 bytes, including length byte.

Oracle Date and Time Data Types

DATE	It is used to store a valid date-time format with a fixed length. Its range varies from January 1, 4712 BC to December 31, 9999 AD.
TIMESTAMP	It is used to store the valid date in YYYY-MM-DD with time hh:mm:ss format.

Oracle Large Object Data Types (LOB Types)

BLOB	It is used to specify unstructured binary data. Its range goes up to 232-1 bytes or 4 GB.
BFILE	It is used to store binary data in an external file. Its range goes up to 232-1 bytes or 4 GB.
CLOB	It is used for single-byte character data. Its range goes up to 232-1 bytes or 4 GB.
NCLOB	It is used to specify single byte or fixed length multibyte national character set (NCHAR) data. Its range is up to 232-1 bytes or 4 GB.
RAW(size)	It is used to specify variable length raw binary data. Its range is up to 2000 bytes per row. Its maximum size must be specified.
LONG RAW	It is used to specify variable length raw binary data. Its range up to 231-1 bytes or 2 GB, per row.

SQL Operators Every database administrator and user uses SQL queries for manipulating and accessing the data of database tables and views. The manipulation and retrieving of the data are performed with the help of reserved words and characters, which are used to perform arithmetic operations, logical operations, comparison operations, compound operations, etc. What is SQL Operator? The SQL reserved words and characters are called operators, which are used with a WHERE clause in a SQL query. In SQL, an operator can either be a unary or binary operator. The unary operator uses only one operand for performing the unary operation, whereas the binary operator uses two operands for performing the binary operation. Syntax of Unary SQL Operator Operator SQL_Operand   Syntax of Unary SQL Operator Operand1 SQL_Operator Operand2   Note: SQL operators are used for filtering the table's data by a specific condition in the SQL statement. What is the Precedence of SQL Operator? The precedence of SQL operators is the sequence in which the SQL evaluates the different operators in the same expression. Structured Query Language evaluates those operators first, which have high precedence. In the following table, the operators at the top have high precedence, and the operators that appear at the bottom have low precedence. SQL Operator Symbols Operators ** Exponentiation operator +, - Identity operator, Negation operator *, / Multiplication operator, Division operator +, -, || Addition (plus) operator, subtraction (minus) operator, String Concatenation operator =, !=, <, >, <=, >=, IS NULL, LIKE, BETWEEN, IN Comparison Operators NOT Logical negation operator && or AND Conjunction operator OR Inclusion operator For Example, UPDATE employee   SET salary = 20 - 3 * 5 WHERE Emp_Id = 5;   In the above SQL example, salary is assigned 5, not 85, because the * (Multiplication) Operator has higher precedence than the - (subtraction) operator, so it first gets multiplied with 3*5 and then subtracts from 20. Types of Operator SQL operators are categorized in the following categories: SQL Arithmetic Operators SQL Comparison Operators SQL Logical Operators SQL Set Operators SQL Bit-wise Operators SQL Unary Operators Let's discuss each operator with their types. SQL Arithmetic Operators The Arithmetic Operators perform the mathematical operation on the numerical data of the SQL tables. These operators perform addition, subtraction, multiplication, and division operations on the numerical operands. Following are the various arithmetic operators performed on the SQL data: SQL Addition Operator (+) SQL Subtraction Operator (-) SQL Multiplication Operator (+) SQL Division Operator (-) SQL Modulus Operator (+) SQL Addition Operator (+) The Addition Operator in SQL performs the addition on the numerical data of the database table. In SQL, we can easily add the numerical values of two columns of the same table by specifying both the column names as the first and second operand. We can also add the numbers to the existing numbers of the specific column. Syntax of SQL Addition Operator: SELECT operand1 + operand2;   Let's understand the below example which explains how to execute Addition Operator in SQL query: This example consists of an Employee_details table, which has four columns Emp_Id, Emp_Name, Emp_Salary, and Emp_Monthlybonus. Emp Id Emp Name Emp Salary Emp Monthlybonus 101 Tushar 25000 4000 102 Anuj 30000 200 Suppose, we want to add 20,000 to the salary of each employee specified in the table. Then, we have to write the following query in the SQL: SELECT Emp_Salary + 20000 as Emp_New_Salary FROM Employee_details;   In this query, we have performed the SQL addition operation on the single column of the given table. Suppose, we want to add the Salary and monthly bonus columns of the above table, then we have to write the following query in SQL: SELECT Emp_Salary + Emp_Monthlybonus as Emp_Total_Salary FROM Employee_details;   In this query, we have added two columns with each other of the above table. SQL Subtraction Operator (-) The Subtraction Operator in SQL performs the subtraction on the numerical data of the database table. In SQL, we can easily subtract the numerical values of two columns of the same table by specifying both the column names as the first and second operand. We can also subtract the number from the existing number of the specific table column. Syntax of SQL Subtraction Operator: SELECT operand1 - operand2;   Let's understand the below example which explains how to execute Subtraction Operator in SQL query: This example consists of an Employee_details table, which has four columns Emp_Id, Emp_Name, Emp_Salary, and Emp_Monthlybonus. Emp Id Emp Name Emp Salary Penalty 201 Abhay 25000 200 202 Sumit 30000 500 Suppose we want to subtract 5,000 from the salary of each employee given in the Employee_details table. Then, we have to write the following query in the SQL: SELECT Emp_Salary - 5000 as Emp_New_Salary FROM Employee_details;   In this query, we have performed the SQL subtraction operation on the single column of the given table. If we want to subtract the penalty from the salary of each employee, then we have to write the following query in SQL: SELECT Emp_Salary - Penalty as Emp_Total_Salary FROM Employee_details;   SQL Multiplication Operator (*) The Multiplication Operator in SQL performs the Multiplication on the numerical data of the database table. In SQL, we can easily multiply the numerical values of two columns of the same table by specifying both the column names as the first and second operand. Syntax of SQL Multiplication Operator: SELECT operand1 * operand2;   Let's understand the below example which explains how to execute Multiplication Operator in SQL query: This example consists of an Employee_details table, which has four columns Emp_Id, Emp_Name, Emp_Salary, and Emp_Monthlybonus. Emp Id Emp Name Emp Salary Penalty 201 Abhay 25000 200 202 Sumit 30000 500 Suppose, we want to double the salary of each employee given in the Employee_details table. Then, we have to write the following query in the SQL: SELECT Emp_Salary * 2 as Emp_New_Salary FROM Employee_details;   In this query, we have performed the SQL multiplication operation on the single column of the given table. If we want to multiply the Emp_Id column to Emp_Salary column of that employee whose Emp_Id is 202, then we have to write the following query in SQL: SELECT Emp_Id * Emp_Salary as Emp_Id * Emp_Salary FROM Employee_details WHERE Emp_Id = 202;   In this query, we have multiplied the values of two columns by using the WHERE clause. SQL Division Operator (/) The Division Operator in SQL divides the operand on the left side by the operand on the right side. Syntax of SQL Division Operator: SELECT operand1 / operand2;   In SQL, we can also divide the numerical values of one column by another column of the same table by specifying both column names as the first and second operand. We can also perform the division operation on the stored numbers in the column of the SQL table. Let's understand the below example which explains how to execute Division Operator in SQL query: This example consists of an Employee_details table, which has three columns Emp_Id, Emp_Name, and Emp_Salary. Emp Id Emp Name Emp Salary 201 Abhay 25000 202 Sumit 30000 Suppose, we want to half the salary of each employee given in the Employee_details table. For this operation, we have to write the following query in the SQL: SELECT Emp_Salary / 2 as Emp_New_Salary FROM Employee_details;   In this query, we have performed the SQL division operation on the single column of the given table. SQL Modulus Operator (%) The Modulus Operator in SQL provides the remainder when the operand on the left side is divided by the operand on the right side. Syntax of SQL Modulus Operator: SELECT operand1 % operand2;   Let's understand the below example which explains how to execute Modulus Operator in SQL query: This example consists of a Division table, which has three columns Number, First_operand, and Second_operand. Number First operand Second operand 1 56 4 2 32 8 3 89 9 4 18 10 5 10 5 If we want to get the remainder by dividing the numbers of First_operand column by the numbers of Second_operand column, then we have to write the following query in SQL: SELECT First_operand % Second_operand as Remainder FROM Employee_details;   SQL Comparison Operators The Comparison Operators in SQL compare two different data of SQL table and check whether they are the same, greater, and lesser. The SQL comparison operators are used with the WHERE clause in the SQL queries Following are the various comparison operators which are performed on the data stored in the SQL database tables: SQL Equal Operator (=) SQL Not Equal Operator (!=) SQL Greater Than Operator (>) SQL Greater Than Equals to Operator (>=) SQL Less Than Operator (<)\ SQL Less Than Equals to Operator (<=) SQL Equal Operator (=) This operator is highly used in SQL queries. The Equal Operator in SQL shows only data that matches the specified value in the query. This operator returns TRUE records from the database table if the value of both operands specified in the query is matched. Let's understand the below example which explains how to execute Equal Operator in SQL query: This example consists of an Employee_details table, which has three columns Emp_Id, Emp_Name, and Emp_Salary. Emp Id Emp Name Emp Salary 201 Abhay 30000 202 Ankit 40000 203 Bheem 30000 204 Ram 29000 205 Sumit 30000 Suppose, we want to access all the records of those employees from the Employee_details table whose salary is 30000. Then, we have to write the following query in the SQL database: SELECT * FROM Employee_details WHERE Emp_Salary = 30000;   In this example, we used the SQL equal operator with WHERE clause for getting the records of those employees whose salary is 30000. SQL Equal Not Operator (!=) The Equal Not Operator in SQL shows only those data that do not match the query's specified value. This operator returns those records or rows from the database views and tables if the value of both operands specified in the query is not matched with each other. Let's understand the below example which explains how to execute Equal Not Operator in SQL query: This example consists of an Employee_details table, which has three columns Emp_Id, Emp_Name, and Emp_Salary. Emp Id Emp Name Emp Salary 201 Abhay 45000 202 Ankit 45000 203 Bheem 30000 204 Ram 29000 205 Sumit 29000 Suppose, we want to access all the records of those employees from the Employee_details table whose salary is not 45000. Then, we have to write the following query in the SQL database: SELECT * FROM Employee_details WHERE Emp_Salary != 45000;   In this example, we used the SQL equal not operator with WHERE clause for getting the records of those employees whose salary is not 45000. SQL Greater Than Operator (>) The Greater Than Operator in SQL shows only those data which are greater than the value of the right-hand operand. Let's understand the below example which explains how to execute Greater ThanOperator (>) in SQL query: This example consists of an Employee_details table, which has three columns Emp_Id, Emp_Name, and Emp_Salary. Emp Id Emp Name Emp Salary 201 Abhay 45000 202 Ankit 45000 203 Bheem 30000 204 Ram 29000 205 Sumit 29000 Suppose, we want to access all the records of those employees from the Employee_details table whose employee id is greater than 202. Then, we have to write the following query in the SQL database: SELECT * FROM Employee_details WHERE Emp_Id > 202;   Here, SQL greater than operator displays the records of those employees from the above table whose Employee Id is greater than 202. SQL Greater Than Equals to Operator (>=) The Greater Than Equals to Operator in SQL shows those data from the table which are greater than and equal to the value of the right-hand operand. Let's understand the below example which explains how to execute greater than equals to the operator (>=) in SQL query: This example consists of an Employee_details table, which has three columns Emp_Id, Emp_Name, and Emp_Salary. Emp Id Emp Name Emp Salary 201 Abhay 45000 202 Ankit 45000 203 Bheem 30000 204 Ram 29000 205 Sumit 29000 Suppose, we want to access all the records of those employees from the Employee_details table whose employee id is greater than and equals to 202. For this, we have to write the following query in the SQL database: SELECT * FROM Employee_details WHERE Emp_Id >= 202;   Here,'SQL greater than equals to operator' with WHERE clause displays the rows of those employees from the table whose Employee Id is greater than and equals to 202. SQL Less Than Operator (<) The Less Than Operator in SQL shows only those data from the database tables which are less than the value of the right-side operand. This comparison operator checks that the left side operand is lesser than the right side operand. If the condition becomes true, then this operator in SQL displays the data which is less than the value of the right-side operand. Let's understand the below example which explains how to execute less than operator (<) in SQL query: This example consists of an Employee_details table, which has three columns Emp_Id, Emp_Name, and Emp_Salary. Emp Id Emp Name Emp Salary 201 Abhay 45000 202 Ankit 45000 203 Bheem 30000 204 Ram 29000 205 Sumit 29000 Suppose, we want to access all the records of those employees from the Employee_details table whose employee id is less than 204. For this, we have to write the following query in the SQL database: SELECT * FROM Employee_details WHERE Emp_Id < 204;   Here,SQL less than operator with WHERE clause displays the records of those employees from the above table whose Employee Id is less than 204. SQL Less Than Equals to Operator (<=) The Less Than Equals to Operator in SQL shows those data from the table which are lesser and equal to the value of the right-side operand. This comparison operator checks that the left side operand is lesser and equal to the right side operand. Let's understand the below example which explains how to execute less than equals to the operator (<=) in SQL query: This example consists of an Employee_details table, which has three columns Emp_Id, Emp_Name, and Emp_Salary. Emp Id Emp Name Emp Salary 201 Abhay 45000 202 Ankit 45000 203 Bheem 30000 204 Ram 29000 205 Sumit 29000 Suppose, we want to access all the records of those employees from the Employee_details table whose employee id is less and equals 203. For this, we have to write the following query in the SQL database: SELECT * FROM Employee_details WHERE Emp_Id <= 203;   Here, SQL less than equals to the operator with WHERE clause displays the rows of those employees from the table whose Employee Id is less than and equals 202. SQL Logical Operators The Logical Operators in SQL perform the Boolean operations, which give two results True and False. These operators provide True value if both operands match the logical condition. Following are the various logical operators which are performed on the data stored in the SQL database tables: SQL ALL operator SQL AND operator SQL OR operator SQL BETWEEN operator SQL IN operator SQL NOT operator SQL ANY operator SQL LIKE operator SQL ALL Operator The ALL operator in SQL compares the specified value to all the values of a column from the sub-query in the SQL database. This operator is always used with the following statement: SELECT, HAVING, and WHERE. Syntax of ALL operator: SELECT column_Name1, ...., column_NameN FROM table_Name WHERE column Comparison_operator ALL (SELECT column FROM tablename2)   Let's understand the below example which explains how to execute ALL logical operators in SQL query: This example consists of an Employee_details table, which has three columns Emp_Id, Emp_Name, Emp_Salary, and Emp_City. Emp Id Emp Name Emp Salary Emp City 201 Abhay 25000 Gurgaon 202 Ankit 45000 Delhi 203 Bheem 30000 Jaipur 204 Ram 29000 Mumbai 205 Sumit 40000 Kolkata If we want to access the employee id and employee names of those employees from the table whose salaries are greater than the salary of employees who lives in Jaipur city, then we have to type the following query in SQL. SELECT Emp_Id, Emp_Name FROM Employee_details WHERE Emp_Salary > ALL ( SELECT Emp_Salary FROM  Employee_details WHERE Emp_City = Jaipur)   Here, we used the SQL ALL operator with greater than the operator. SQL AND Operator The AND operator in SQL would show the record from the database table if all the conditions separated by the AND operator evaluated to True. It is also known as the conjunctive operator and is used with the WHERE clause. Syntax of AND operator: SELECT column1, ...., columnN FROM table_Name WHERE condition1 AND condition2 AND condition3 AND ....... AND conditionN;   Let's understand the below example which explains how to execute AND logical operator in SQL query: This example consists of an Employee_details table, which has three columns Emp_Id, Emp_Name, Emp_Salary, and Emp_City. Emp Id Emp Name Emp Salary Emp City 201 Abhay 25000 Delhi 202 Ankit 45000 Chandigarh 203 Bheem 30000 Delhi 204 Ram 25000 Delhi 205 Sumit 40000 Kolkata Suppose, we want to access all the records of those employees from the Employee_details table whose salary is 25000 and the city is Delhi. For this, we have to write the following query in SQL: SELECT * FROM Employee_details WHERE Emp_Salary = 25000 OR Emp_City = 'Delhi';    Here,SQL AND operator with WHERE clause shows the record of employees whose salary is 25000 and the city is Delhi. SQL OR Operator The OR operator in SQL shows the record from the table if any of the conditions separated by the OR operator evaluates to True. It is also known as the conjunctive operator and is used with the WHERE clause. Syntax of OR operator: SELECT column1, ...., columnN FROM table_Name WHERE condition1 OR condition2 OR condition3 OR ....... OR conditionN;   Let's understand the below example which explains how to execute OR logical operator in SQL query: This example consists of an Employee_details table, which has three columns Emp_Id, Emp_Name, Emp_Salary, and Emp_City. Emp Id Emp Name Emp Salary Emp City 201 Abhay 25000 Delhi 202 Ankit 45000 Chandigarh 203 Bheem 30000 Delhi 204 Ram 25000 Delhi 205 Sumit 40000 Kolkata If we want to access all the records of those employees from the Employee_details table whose salary is 25000 or the city is Delhi. For this, we have to write the following query in SQL: SELECT * FROM Employee_details WHERE Emp_Salary = 25000 OR Emp_City = 'Delhi';    Here, SQL OR operator with WHERE clause shows the record of employees whose salary is 25000 or the city is Delhi. SQL BETWEEN Operator The BETWEEN operator in SQL shows the record within the range mentioned in the SQL query. This operator operates on the numbers, characters, and date/time operands. If there is no value in the given range, then this operator shows NULL value. Syntax of BETWEEN operator: SELECT column_Name1, column_Name2 ...., column_NameN FROM table_Name WHERE column_nameBETWEEN value1 and value2;   Let's understand the below example which explains how to execute BETWEEN logical operator in SQL query: This example consists of an Employee_details table, which has three columns Emp_Id, Emp_Name, Emp_Salary, and Emp_City. Emp Id Emp Name Emp Salary Emp City 201 Abhay 25000 Delhi 202 Ankit 45000 Chandigarh 203 Bheem 30000 Delhi 204 Ram 25000 Delhi 205 Sumit 40000 Kolkata Suppose, we want to access all the information of those employees from the Employee_details table who is having salaries between 20000 and 40000. For this, we have to write the following query in SQL: SELECT * FROM Employee_details WHERE Emp_Salary BETWEEN 30000 AND 45000;    Here, we used the SQL BETWEEN operator with the Emp_Salary field. SQL IN Operator The IN operator in SQL allows database users to specify two or more values in a WHERE clause. This logical operator minimizes the requirement of multiple OR conditions. This operator makes the query easier to learn and understand. This operator returns those rows whose values match with any value of the given list. Syntax of IN operator: SELECT column_Name1, column_Name2 ...., column_NameN FROM table_Name WHERE column_name IN (list_of_values);   Let's understand the below example which explains how to execute IN logical operator in SQL query: This example consists of an Employee_details table, which has three columns Emp_Id, Emp_Name, Emp_Salary, and Emp_City. Emp Id Emp Name Emp Salary Emp City 201 Abhay 25000 Delhi 202 Ankit 45000 Chandigarh 203 Bheem 30000 Delhi 204 Ram 25000 Delhi 205 Sumit 40000 Kolkata Suppose, we want to show all the information of those employees from the Employee_details table whose Employee Id is 202, 204, and 205. For this, we have to write the following query in SQL: SELECT * FROM Employee_details WHERE Emp_Id IN (202, 204, 205);   Here, we used the SQL IN operator with the Emp_Id column. Suppose, we want to show all the information of those employees from the Employee_details table whose Employee Id is not equal to 202 and 205. For this, we have to write the following query in SQL: SELECT * FROM Employee_details WHERE Emp_Id NOT IN (202,205);              Here, we used the SQL NOT IN operator with the Emp_Id column. SQL NOT Operator The NOT operator in SQL shows the record from the table if the condition evaluates to false. It is always used with the WHERE clause. Syntax of NOT operator: SELECT column1, column2 ...., columnN FROM table_Name WHERE NOT condition;   Let's understand the below example which explains how to execute NOT logical operator in SQL query: This example consists of an Employee_details table, which has four columns Emp_Id, Emp_Name, Emp_Salary, and Emp_City. Emp Id Emp Name Emp Salary Emp City 201 Abhay 25000 Delhi 202 Ankit 45000 Chandigarh 203 Bheem 30000 Delhi 204 Ram 25000 Delhi 205 Sumit 40000 Kolkata Suppose, we want to show all the information of those employees from the Employee_details table whose Cityis not Delhi. For this, we have to write the following query in SQL: SELECT * FROM Employee_details WHERE NOT Emp_City = 'Delhi' ;   In this example, we used the SQL NOT operator with the Emp_City column. Suppose, we want to show all the information of those employees from the Employee_details table whose Cityis not Delhi and Chandigarh. For this, we have to write the following query in SQL: SELECT * FROM Employee_details WHERE NOT Emp_City = 'Delhi' AND NOT Emp_City = 'Chandigarh';    In this example, we used the SQL NOT operator with the Emp_City column. SQL ANY Operator The ANY operator in SQL shows the records when any of the values returned by the sub-query meet the condition. The ANY logical operator must match at least one record in the inner query and must be preceded by any SQL comparison operator. Syntax of ANY operator: SELECT column1, column2 ...., columnN FROM table_Name WHERE column_name comparison_operator ANY ( SELECT column_name FROM table_name WHERE condition(s)) ;   SQL LIKE Operator The LIKE operator in SQL shows those records from the table which match with the given pattern specified in the sub-query. The percentage (%) sign is a wildcard which is used in conjunction with this logical operator. This operator is used in the WHERE clause with the following three statements: SELECT statement UPDATE statement DELETE statement Syntax of LIKE operator: SELECT column_Name1, column_Name2 ...., column_NameN FROM table_Name WHERE column_name LIKE pattern;   Let's understand the below example which explains how to execute LIKE logical operator in SQL query: This example consists of an Employee_details table, which has four columns Emp_Id, Emp_Name, Emp_Salary, and Emp_City. Emp Id Emp Name Emp Salary Emp City 201 Sanjay 25000 Delhi 202 Ajay 45000 Chandigarh 203 Saket 30000 Delhi 204 Abhay 25000 Delhi 205 Sumit 40000 Kolkata If we want to show all the information of those employees from the Employee_details whose name starts with ''s''. For this, we have to write the following query in SQL: SELECT * FROM Employee_details WHERE Emp_Name LIKE 's%' ;    In this example, we used the SQL LIKE operator with Emp_Name column because we want to access the record of those employees whose name starts with s. If we want to show all the information of those employees from the Employee_detailswhose name ends with ''y''. For this, we have to write the following query in SQL: SELECT * FROM Employee_details WHERE Emp_Name LIKE '%y' ;    If we want to show all the information of those employees from the Employee_detailswhose name starts with ''S'' and ends with ''y''. For this, we have to write the following query in SQL: SELECT * FROM Employee_details WHERE Emp_Name LIKE 'S%y' ;    SQL Set Operators The Set Operators in SQL combine a similar type of data from two or more SQL database tables. It mixes the result, which is extracted from two or more SQL queries, into a single result. Set operators combine more than one select statement in a single query and return a specific result set. Following are the various set operators which are performed on the similar data stored in the two SQL database tables: SQL Union Operator SQL Union ALL Operator SQL Intersect Operator SQL Minus Operator SQL Union Operator The SQL Union Operator combines the result of two or more SELECT statements and provides the single output. The data type and the number of columns must be the same for each SELECT statement used with the UNION operator. This operator does not show the duplicate records in the output table. Syntax of UNION Set operator: SELECT column1, column2 ...., columnN FROM table_Name1 [WHERE conditions]     UNION    SELECT column1, column2 ...., columnN FROM table_Name2 [WHERE conditions];   Let's understand the below example which explains how to execute Union operator in Structured Query Language: In this example, we used two tables. Both tables have four columns Emp_Id, Emp_Name, Emp_Salary, and Emp_City. Emp Id Emp Name Emp Salary Emp City 201 Sanjay 25000 Delhi 202 Ajay 45000 Delhi 203 Saket 30000 Aligarh Table: Employee_details1 Emp Id Emp Name Emp Salary Emp City 203 Saket 30000 Aligarh 204 Saurabh 40000 Delhi 205 Ram 30000 Kerala 201 Sanjay 25000 Delhi Table: Employee_details2 Suppose, we want to see the employee name and employee id of each employee from both tables in a single output. For this, we have to write the following query in SQL: SELECT Emp_ID, Emp_Name FROM Employee_details1   UNION   SELECT Emp_ID, Emp_Name FROM Employee_details2 ;   SQL Union ALL Operator The SQL Union Operator is the same as the UNION operator, but the only difference is that it also shows the same record. Syntax of UNION ALL Set operator: SELECT column1, column2 ...., columnN FROM table_Name1 [WHERE conditions]     UNION ALL   SELECT column1, column2 ...., columnN FROM table_Name2 [WHERE conditions];   Let's understand the below example which explains how to execute Union ALL operator in Structured Query Language: In this example, we used two tables. Both tables have four columns Emp_Id, Emp_Name, Emp_Salary, and Emp_City. Emp Id Emp Name Emp Salary Emp City 201 Sanjay 25000 Delhi 202 Ajay 45000 Delhi 203 Saket 30000 Aligarh Table: Employee_details1 Emp Id Emp Name Emp Salary Emp City 203 Saket 30000 Aligarh 204 Saurabh 40000 Delhi 205 Ram 30000 Kerala 201 Sanjay 25000 Delhi Table: Employee_details2 If we want to see the employee name of each employee of both tables in a single output. For this, we have to write the following query in SQL: SELECT Emp_Name FROM Employee_details1   UNION ALL   SELECT Emp_Name FROM Employee_details2 ;   SQL Intersect Operator The SQL Intersect Operator shows the common record from two or more SELECT statements. The data type and the number of columns must be the same for each SELECT statement used with the INTERSECT operator. Syntax of INTERSECT Set operator: SELECT column1, column2 ...., columnN FROM table_Name1 [WHERE conditions]     INTERSECT   SELECT column1, column2 ...., columnN FROM table_Name2 [WHERE conditions];   Let's understand the below example which explains how to execute INTERSECT operator in Structured Query Language: In this example, we used two tables. Both tables have four columns Emp_Id, Emp_Name, Emp_Salary, and Emp_City. Emp Id Emp Name Emp Salary Emp City 201 Sanjay 25000 Delhi 202 Ajay 45000 Delhi 203 Saket 30000 Aligarh Table: Employee_details1 Emp Id Emp Name Emp Salary Emp City 203 Saket 30000 Aligarh 204 Saurabh 40000 Delhi 205 Ram 30000 Kerala 201 Sanjay 25000 Delhi Table: Employee_details2 Suppose, we want to see a common record of the employee from both the tables in a single output. For this, we have to write the following query in SQL: SELECT Emp_Name FROM Employee_details1   INTERSECT   SELECT Emp_Name FROM Employee_details2 ;   SQL Minus Operator The SQL Minus Operator combines the result of two or more SELECT statements and shows only the results from the first data set. Syntax of MINUS operator: SELECT column1, column2 ...., columnN FROM First_tablename [WHERE conditions]     MINUS   SELECT column1, column2 ...., columnN FROM Second_tablename [WHERE conditions];   Let's understand the below example which explains how to execute INTERSECT operator in Structured Query Language: In this example, we used two tables. Both tables have four columns Emp_Id, Emp_Name, Emp_Salary, and Emp_City. Emp Id Emp Name Emp Salary Emp City 201 Sanjay 25000 Delhi 202 Ajay 45000 Delhi 203 Saket 30000 Aligarh Table: Employee_details1 Emp Id Emp Name Emp Salary Emp City 203 Saket 30000 Aligarh 204 Saurabh 40000 Delhi 205 Ram 30000 Kerala 201 Sanjay 25000 Delhi Table: Employee_details2 Suppose, we want to see the name of employees from the first result set after the combination of both tables. For this, we have to write the following query in SQL: SELECT Emp_Name FROM Employee_details1   MINUS   SELECT Emp_Name FROM Employee_details2 ;   SQL Unary Operators The Unary Operators in SQL perform the unary operations on the single data of the SQL table, i.e., these operators operate only on one operand. These types of operators can be easily operated on the numeric data value of the SQL table. Following are the various unary operators which are performed on the numeric data stored in the SQL table: SQL Unary Positive Operator SQL Unary Negative Operator SQL Unary Bitwise NOT Operator SQL Unary Positive Operator The SQL Positive (+) operator makes the numeric value of the SQL table positive. Syntax of Unary Positive Operator SELECT +(column1), +(column2) ...., +(columnN) FROM table_Name [WHERE conditions] ;   Let's understand the below example which explains how to execute a Positive unary operator on the data of SQL table: This example consists of anEmployee_details table, which has four columns Emp_Id, Emp_Name, Emp_Salary, and Emp_City. Emp Id Emp Name Emp Salary Emp City 201 Sanjay 25000 Delhi 202 Ajay 45000 Chandigarh 203 Saket 30000 Delhi 204 Abhay 25000 Delhi 205 Sumit 40000 Kolkata Suppose, we want to see the salary of each employee as positive from the Employee_details table. For this, we have to write the following query in SQL: SELECT  +Emp_Salary Employee_details ;   SQL Unary Negative Operator The SQL Negative (-) operator makes the numeric value of the SQL table negative. Syntax of Unary Negative Operator SELECT -(column_Name1), -(column_Name2) ...., -(column_NameN) FROM table_Name [WHERE conditions] ;   Let's understand the below example which explains how to execute Negative unary operator on the data of SQL table: This example consists of an Employee_details table, which has four columns Emp_Id, Emp_Name, Emp_Salary, and Emp_City. Emp Id Emp Name Emp Salary Emp City 201 Sanjay 25000 Delhi 202 Ajay 45000 Chandigarh 203 Saket 30000 Delhi 204 Abhay 25000 Delhi 205 Sumit 40000 Kolkata Suppose, we want to see the salary of each employee as negative from the Employee_details table. For this, we have to write the following query in SQL: SELECT -Emp_Salary Employee_details ;   Suppose, we want to see the salary of those employees as negative whose city is Kolkatain the Employee_details table. For this, we have to write the following query in SQL: SELECT -Emp_Salary Employee_details WHERE Emp_City = 'Kolkata';   SQL Bitwise NOT Operator The SQL Bitwise NOT operator provides the one's complement of the single numeric operand. This operator turns each bit of numeric value. If the bit of any numerical value is 001100, then this operator turns these bits into 110011. Syntax of Bitwise NOT Operator SELECT ~(column1), ~(column2) ...., ~(columnN) FROM table_Name [WHERE conditions] ;   Let's understand the below example which explains how to execute the Bitwise NOT operator on the data of SQL table: This example consists of aStudent_details table, which has four columns Roll_No, Stu_Name, Stu_Marks, and Stu_City. Emp Id Stu Name Stu Marks Stu City 101 Sanjay 85 Delhi 102 Ajay 97 Chandigarh 103 Saket 45 Delhi 104 Abhay 68 Delhi 105 Sumit 60 Kolkata If we want to perform the Bitwise Not operator on the marks column of Student_details, we have to write the following query in SQL: SELECT ~Stu_Marks Employee_details ;   SQL Bitwise Operators The Bitwise Operators in SQL perform the bit operations on the Integer values. To understand the performance of Bitwise operators, you just knew the basics of Boolean algebra. Following are the two important logical operators which are performed on the data stored in the SQL database tables: Bitwise AND (&) Bitwise OR(|) Bitwise AND (&) The Bitwise AND operator performs the logical AND operation on the given Integer values. This operator checks each bit of a value with the corresponding bit of another value. Syntax of Bitwise AND Operator SELECT column1 & column2 & .... & columnN FROM table_Name [WHERE conditions] ;   Let's understand the below example which explains how to execute Bitwise AND operator on the data of SQL table: This example consists of the following table, which has two columns. Each column holds numerical values. When we use the Bitwise AND operator in SQL, then SQL converts the values of both columns in binary format, and the AND operation is performed on the converted bits. After that, SQL converts the resultant bits into user understandable format, i.e., decimal format. Column1 Column2 1 1 2 5 3 4 4 2 5 3 Suppose, we want to perform the Bitwise AND operator between both the columns of the above table. For this, we have to write the following query in SQL: SELECT Column1 & Column2 From TABLE_AND ;   Bitwise OR (|) The Bitwise OR operator performs the logical OR operation on the given Integer values. This operator checks each bit of a value with the corresponding bit of another value. Syntax of Bitwise OR Operator SELECT column1 | column2 | .... | columnN FROM table_Name [WHERE conditions] ;   Let's understand the below example which explains how to execute Bitwise OR operator on the data of SQL table: This example consists of a table that has two columns. Each column holds numerical values. When we used the Bitwise OR operator in SQL, then SQL converts the values of both columns in binary format, and the OR operation is performed on the binary bits. After that, SQL converts the resultant binary bits into user understandable format, i.e., decimal format. Column1 Column2 1 1 2 5 3 4 4 2 5 3 Suppose, we want to perform the Bitwise OR operator between both the columns of the above table. For this, we have to write the following query in SQL: SELECT Column1 | Column2 From TABLE_OR ;   SQL Create Database In SQL, the 'Create Database' statement is a first step for storing the structured data in the database. The database developers and the users use this statement in SQL for creating the new database in the database systems. It creates the database with the name which has been specified in the Create Database statement. Syntax of Create Database statement in SQL CREATE DATABASE Database_Name;   In this syntax, Database_Name specifies the name of the database which we want to create in the system. We have to type the database name in query just after the 'Create Database' keyword. Following are the most important points which are required to learn while creating a database: The database we want to create should be a simple and unique name, which can be easily identified. Database name should be no more than 128 characters. Syntax of Create Database statement in MySQL The same command is used in MySQL to create the new database for storing the structured data. CREATE DATABASE Database_Name;   Syntax of Create Database in Oracle There is no need to create the database in Oracle systems. In the Oracle database, we can directly create the database tables. Examples of Create Database statement in SQL In this article, we took the following two examples which will help how to run and perform the Create Database query in SQL: Example 1: This example creates the Student database. To create the Student database, you have to type the following command in Structured Query Language: CREATE DATABASE Student ;   When this query is executed successfully, then it will show the following output: Database created successfully You can also verify that your database is created in SQL or not by using the following query: SHOW DATABASE ;   SQL does not allow developers to create the database with the existing database name. Suppose if you want to create another Student database in the same database system, then the Create Database statement will show the following error in the output: Can't create database 'Student'; database exists So, firstly you have to delete the existing database by using the Drop Statement. You can also replace the existing database with the help of Replace keyword. If you want to replace the existing Student database, then you have to type the following SQL query: CREATE OR REPLACE DATABASE Student ;   Example 2: Suppose, we want to create the Employee database in the system. Firstly, we have to type the following command in Structured Query Language: CREATE DATABASE Employee ;   When this query is executed successfully, then it will show the following output: Database created successfully You can also check that your database is created in SQL by typing the following query: SHOW DATABASE ;   We know that SQL does not allow developers to create the database with the existing database name. Suppose, we want to create another Employee database in the same database system, firstly, we have to delete the existing database using a drop statement, or we have to replace the existing Employee database with the help of the 'replace' keyword. To replace the existing Employee database with a new Employee database, we have to type the following query in SQL: CREATE OR REPLACE DATABASE Employee;   SQL DROP Database The SQL Drop Database statement deletes the existing database permanently from the database system. This statement deletes all the views and tables if stored in the database, so be careful while using this query in SQL. Following are the most important points which are required to learn before removing the database from the database system: This statement deletes all the data from the database. If you want to restore the deleted data in the future, you should keep the backup of data of that database which you want to delete. Another most important point is that you cannot delete that database from the system which is currently in use by another database user. If you do so, then the drop statement shows the following error on screen: Cannot drop database "name_of_the_database" because it is currently in use.   Syntax of Drop Database Statement in SQL DROP DATABASE Database_Name;   In this SQL syntax, we have to specify the name of that database which we want to delete permanently from the database system. We have to write the name of the database after the DROP DATABASE keyword in every example. We can also delete multiple databases easily by using the single DROP syntax: DROP DATABASE Database_Name1, [ Database_Name2, ......., Database_NameN ] ;   Using this statement, we have no need to write multiple statements for deleting multiple databases. We can specify all the databases by using a comma in a single statement, as shown in the above syntax. Examples of Drop Database Statement in SQL In this article, we took the following two examples that will help how to run and perform the Drop Database query in SQL: Example1: Suppose, we want to delete the Student database with all its data from the database system so, firstly we have to check that the Student database exists in the system or not by using the following statement: SHOW DATABASES ;   If the Student database is shown in the output, then we have to type the following query in SQL for removing the Student database: DROP DATABASE Student;   If the Student database does not exist in the database system and we run the above query in SQL, then the query will show the following output: Can't drop database 'Student'; database doesn't exist Example2: Suppose, we want to delete the College database with all its tables and views from the database system, firstly we have to check that if the College database exists in the system or not by using the following statement: SHOW DATABASES;   If the College database is shown in the output, then you have to type the following query in SQL for removing the College database permanently: DROP DATABASE College;   If the College database does not exist in the database system, and we run the above query in SQL, then this query will show the following output: Can't drop database 'College'; database doesn't exist SQL RENAME Database In some situations, database users and administrators want to change the name of the database for some technical reasons. So, the Rename Database statement in SQL is used to change the name of the existing database. Sometimes, the Rename Database statement is used because the developers think that the original name is not more relevant to the data of the database, or they want to give a temporary name to that database. Syntax of Rename Database in SQL ALTER DATABASE old_database_name MODIFY NAME = new_database_name;   EXEC sp_renamedb'old_database_name' , 'new_database_name'   Syntax of Rename Database in MySQL RENAME DATABASE old_database_name TO new_database_name;    This syntax is used when we want to change the name of the database in MySQL. Examples of Rename Database in SQL In this article, we have taken the following two examples which will help you how to run and perform the Rename Database query in SQL: Example 1: Suppose we want to rename the Student Database. For this, we have to type the following query in SQL: ALTER DATABASE Student MODIFY NAME = College ;   This query will change the name of the database from Student to College. To run this query, we must ensure that the database Student exists in the current database server. If not, then it will show an error in the output. Example 2: Suppose we want to rename the Department Database. For this, we have to type the following query in SQL: ALTER DATABASE Department MODIFY NAME = Company ;   This query changes the name of the database from Department to Company. To run this query, we must ensure that the database Department exists in the current database server. If not, then it will show an error in the output. SQL SELECT Database Suppose database users and administrators want to perform some operations on tables, views, and indexes on the specific existing database in SQL. Firstly, they have to select the database on which they want to run the database queries. Any database user and administrator can easily select the particular database from the current database server using the USE statement in SQL. Syntax of USE statement in SQL USE database_name;    In this syntax, we have to define the name of the database after the USE keyword and the name of the database must be unique. Syntax of USE statement in MySQL USE database_name;    Syntax of USE statement in Oracle There is no need to select the database in Oracle. Examples of USE statement in SQL In this article, we have taken the following three examples which will help you how to run and perform USE statement in SQL: Example 1: Suppose, you want to work with the Hospital database. For this firstly, you have to check that if the Hospital database exists on the current database server or not by using the following query: SHOW DATABASES;   If the Hospital database is shown in the output, then you have to execute the following query to select the Hospital database: USE Hospital;   Example 2: Suppose, you want to work with another College database in SQL. For this firstly, you have to check that the College database exists on the current database server or not by using the following query: SHOW DATABASES;   If the College database is shown in the result, then you have to execute the following query to select the College database: USE College;   Example 3: Suppose you want to work with another School database in SQL. For this firstly, you have to check that the School database exists on the current database server or not by using the following query: SHOW DATABASES;   If the School database is shown in the result, then you have to execute the following query to select the School database: USE School;   SQL Table Table is a collection of data, organized in terms of rows and columns. In DBMS term, table is known as relation and row as tuple. Note: A table has a specified number of columns, but can have any number of rows. Table is the simple form of data storage. A table is also considered as a convenient representation of relations. Let's see an example of an employee table: Employee EMP_NAME ADDRESS SALARY Ankit Lucknow 15000 Raman Allahabad 18000 Mike New York 20000 In the above table, "Employee" is the table name, "EMP_NAME", "ADDRESS" and "SALARY" are the column names. The combination of data of multiple columns forms a row e.g. "Ankit", "Lucknow" and 15000 are the data of one row. SQL TABLE Variable The SQL Table variable is used to create, modify, rename, copy and delete tables. Table variable was introduced by Microsoft. It was introduced with SQL server 2000 to be an alternative of temporary tables. It is a variable where we temporary store records and results. This is same like temp table but in the case of temp table we need to explicitly drop it. Table variables are used to store a set of records. So declaration syntax generally looks like CREATE TABLE syntax. create table "tablename"   ("column1" "data type",   "column2" "data type",   ...   "columnN" "data type");   When a transaction rolled back the data associated with table variable is not rolled back. A table variable generally uses lesser resources than a temporary variable. Table variable cannot be used as an input or an output parameter. Topics of SQL TABLE Statement SQL TABLE Variable What TABLE variable can do? SQL CREATE TABLE How to create a table using SQL query> SQL DROP TABLE How to drop a table? SQL DELETE TABLE How to delete all the records of a table? SQL RENAME TABLE How to rename a table? SQL TRUNCATE TABLE How to truncate a table? SQL COPY TABLE How to copy a table? SQL TEMP TABLE What is temporary table? What are the advantage of temporary table? SQL ALTER TABLE How to add, modify, rename and drop column.