Filtering with WHERE

The WHERE clause in SQL is used to filter rows based on a condition.

Rather than returning all records in a table, WHERE lets you retrieve only the rows that meet your criteria.

Basic WHERE Syntax

Here's the structure of a SELECT query using WHERE:

Basic WHERE Syntax

SELECT column1, column2
FROM table_name
WHERE condition;

• SELECT specifies the columns to display
• FROM selects the table to query
• WHERE filters rows that meet the condition

Example: Filter Students by Exam Score

Let's say the teacher wants a list of students who scored above 90 on the final exam:

Filter students with score > 90

SELECT name, exam_score
FROM final_exam
WHERE exam_score > 90;

This would return:

name	exam_score
Emily Davis	95
Ethan Brown	93

Common Comparison Operators

You can use many operators in the WHERE clause:

• = equal to
• != or <> not equal to
• > greater than
• < less than
• >= greater than or equal to
• <= less than or equal to

You can also combine multiple conditions using AND, OR, and NOT.

Why filtering with WHERE matters

Filtering data helps you answer real questions, such as:

• Which students passed the exam?
• Who scored above 90?
• What records match specific criteria?

WHERE gives you control over your queries and helps you explore meaningful patterns in data.

Try it Yourself!

Filter students who passed the final exam

SELECT name, passed
FROM final_exam
WHERE passed = 'Yes';

This query returns the students who passed the final exam:

name	passed
Emily Davis	Yes
Ethan Brown	Yes