CASE keyword

Syntax#

Flow chart showing the syntax of CASE

Description#

CASE goes through a set of conditions and returns a value corresponding to the first condition met. Each new condition follows the WHEN condition THEN value syntax. The user can define a return value when no condition is met using ELSE. If ELSE is not defined and no conditions are met, then case returns null.

Examples#

Assume the following data

name	age
Tom	4
Jerry	19
Anna	25
Jack	8

CASE with ELSE

SELECT
name,
CASE
    WHEN age > 18 THEN 'major'
    ELSE 'minor'
END
FROM my_table

Result

name	case
Tom	minor
Jerry	major
Anna	major
Jack	minor

CASE without ELSE

SELECT
name,
CASE
    WHEN age > 18 THEN 'major'
END
FROM my_table

Result

name	case
Tom	null
Jerry	major
Anna	major
Jack	null