The WHERE clause is used to filter the records. It helps to extract only those records which satisfy a given condition. For example in the student table, to display the list of students of age18 and above in alphabetical order of their names, the command is given as below:
SELECT * FROM Student WHERE Age>=18 ORDER BY Name;

The NULL value in a field can be searched in a table using the ISNULL in the WHERE clause. For example to list all the students whose Age contains no value, the command is used as: SELECT * FROM Student WHERE Age IS NULL;

The WHERE clause in the SELECT command specifies the criteria for getting the desired result. The general form of SELECT command with WHERE Clause is:
Syntax:
SELECT < column-name > [ < co umn-name > ,.... ] FROM < table-name > WHERE condition > ;

Data query language: The Data Query Language consist of commands used to query or retrieve data from a database. One such SQL command in Data Query Language is
Select - It displays the records from the table.

(i) The Structured Query Language (SQL) is a standard programming language to access and manipulate databases.
(ii) SQL allows the user to create, retrieve, alter, and transfer information among databases.
(iii) It is a language designed for managing and accessing data in a Relational Data Base Management System (RDBMS).