How To Use Case Statement In SQL

In this article, we will learn how to use the Case statement in SQL.

In SQL, the CASE statement goes through conditions and when the first condition is met it returns a value. So, once a condition is true, it will stop reading and return the result. If no conditions are true, it returns the value in the ELSE clause (like an If Else statement).

It returns NULL if there is no ELSE part and no conditions are true.

Syntax

SELECT column_name(s),
CASE
    WHEN <condition1> THEN 'result1'
    WHEN <condition2> THEN 'result2'
    WHEN <conditionN> THEN 'resultN'
    ELSE 'result'
END
FROM TABLE_NAME;

Example

The subsequent statement would go through conditions and returns a value when the first condition is met:

SELECT *,
CASE 
    WHEN Age > 18 THEN 'The Age is greater than 18.'
    WHEN Age < 18 THEN 'The Age is under 18.'
    ELSE 'The Age is 18.'
END AS AgeText
FROM StudentInfo;

Also, check How To Use If Else Statement In SQL