CASE Expressions

The CASE expression lets you add conditional logic to your SQL queries.

It's like using if or switch statements in programming. You can return different values depending on conditions.

Syntax

You can use CASE to add conditional logic to your SQL queries.

CASE syntax

CASE
  WHEN condition1 THEN result1
  WHEN condition2 THEN result2
  ...
  ELSE default_result
END

You can use CASE inside SELECT, ORDER BY, WHERE, and even inside window functions.

Example: Course Progress Status

Let's use the CodeFriends dataset to categorize users based on how far they've progressed in a course.

course_progress

user_id	course_name	progress_percent
1	SQL Basics	100
2	SQL Basics	85
3	SQL Basics	70
4	SQL Basics	55
5	SQL Basics	30

We can use CASE to assign each user a label:

Assigning Course Completion Status

SELECT user_id,
  course_name,
  progress_percent,
  CASE
    WHEN progress_percent = 100 THEN 'Completed'
    WHEN progress_percent >= 75 THEN 'Almost done'
    WHEN progress_percent >= 50 THEN 'Halfway'
    ELSE 'Just started'
  END AS completion_status
FROM course_progress;

Result:

user_id	course_name	progress_percent	completion_status
1	SQL Basics	100	Completed
2	SQL Basics	85	Almost done
3	SQL Basics	70	Halfway
4	SQL Basics	55	Halfway
5	SQL Basics	30	Just started

How to use CASE

With CASE, you can categorize or label data based on rules, replace values conditionally, and add logic directly into your queries without writing extra code.

It's especially useful in reporting, dashboards, and analysis tasks.

Want to learn more?

Join CodeFriends Plus membership or enroll in a course to start your journey.

Learn moreSign In