SQL WHERE | Filtering Records with Conditions

WHERE

In real life, when you search for something, you rarely want everything.

For example:

From a phone contact list, you search only one name

From an online store, you filter only laptops under ₹50,000

From student records, you look for students who passed

Databases work in the same way.

A database table may contain thousands or millions of records, but most of the time we need only specific data, not the entire table.

This is where filtering records becomes important.

What Is Filtering in SQL?

Filtering means selecting only those rows (records) that match a specific condition.

SQL provides the WHERE clause to apply such conditions.

The WHERE clause is used to filter records based on given conditions.

What Is the WHERE Clause?

The WHERE clause is used in SQL to restrict the data returned by a query.

Instead of fetching all rows from a table, the WHERE clause allows you to:

Select specific records

Apply conditions

Get meaningful results

Syntax

SELECT column1, column2
FROM table_name
WHERE condition;

Explanation

SELECT - specifies the columns to display

FROM - specifies the table

WHERE - applies the condition

condition - decides which rows to include

Example: Students Table

id	name	age	city
1	Rahul	20	Delhi
2	Neha	22	Mumbai
3	Amit	20	Delhi
4	Priya	21	Pune

Example - 1: Filter Records Using WHERE

Query: Select students who are 20 years old

SELECT *
FROM students
WHERE age = 20;

Output

id name age city
1 Rahul 20 Delhi
3 Amit 20 Delhi

Only records matching the condition are returned.

Example - 2: Filtering Using Text Values

Query: Select students from Delhi

SELECT name, age
FROM students
WHERE city = 'Delhi';

Explanation

Text values are written inside single quotes

Only students whose city is Delhi are selected

Common Comparison Operators Used with WHERE

Operator	Meaning
=	Equal to
!= or <>	Not equal to
>	Greater than
<	Less than
>=	Greater than or equal to
<=	Less than or equal to

Example - 3: Using Comparison Operations

Query: Select students older than 20

SELECT *
FROM students
WHERE age > 20;

Important Points About WHERE Clause

WHERE clause filters rows, not columns
It works with:

1. Numbers

2. Text

3. Dates

Conditions are evaluated row by row
Without WHERE, all records are returned

WHERE Clause with SELECT, UPDATE, DELETE

SELECT - filters displayed data

UPDATE - filters rows to update

DELETE - filters rows to delete

Using WHERE incorrectly can update or delete all records, so it must be used carefully.

Two Minute Drill

WHERE clause is used to filter records
It limits rows returned by a query
Works with numbers, text and conditions
Always written after FROM
Conditions decide which rows are selected
Text values use single quotes
Without WHERE, all records are selected