WHERE Clause

The WHERE clause in SQL is used to filter records that meet a specified condition. It allows you to limit the result set to only those rows that match the given criteria. You can use operators such as =, >, <, LIKE, IN, BETWEEN, and more to filter data effectively.

Basic Syntax

SELECT column1, column2, ...
FROM table_name
WHERE condition;

1. Filtering by Equality (=)

Retrieve records that match a specific value.

Example:

SELECT * FROM Employees WHERE DepartmentID = 101;

This query retrieves all employees who are in department 101.

2. Filtering by Greater Than (>) or Less Than (<)

Filter records where values are greater than or less than a certain value.

Example:

SELECT * FROM Employees WHERE Salary > 50000;

This query retrieves all employees with a salary greater than 50,000.

3. Using AND and OR to Combine Conditions

You can combine multiple conditions using the AND and OR operators.

Example (Using AND):

SELECT * FROM Employees WHERE DepartmentID = 101 AND Salary > 50000;

This query retrieves employees in department 101 who also have a salary greater than 50,000.

Example (Using OR):

SELECT * FROM Employees WHERE DepartmentID = 101 OR DepartmentID = 102;

SELECT * FROM Employees WHERE DepartmentID IN (101, 102, 103);

SELECT * FROM Employees WHERE Salary BETWEEN 40000 AND 60000;