Example
Go through conditions and return a value when the first condition is met:
SELECT OrderID, Quantity,
CASE
WHEN Quantity > 30 THEN "The quantity is greater than 30"
WHEN Quantity = 30 THEN "The quantity is 30"
ELSE "The quantity is under 30"
END
FROM OrderDetails;
Definition and Usage
The CASE statement goes through conditions and return a value when the first condition is met (like an IF-THEN-ELSE statement). So, once a condition is true, it will stop reading and return the result.
If no conditions are true, it will return the value in the ELSE clause.
If there is no ELSE part and no conditions are true, it returns NULL.
Syntax
CASE
WHEN condition1 THEN result1
WHEN condition2 THEN result2
WHEN conditionN THEN resultN
ELSE result
END;