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case

case

description

Syntax

CASE expression
WHEN condition1 THEN result1
[WHEN condition2 THEN result2]
...
[WHEN conditionN THEN resultN]
[ELSE result]
END

OR

CASE WHEN condition1 THEN result1
[WHEN condition2 THEN result2]
...
[WHEN conditionN THEN resultN]
[ELSE result]
END

Compare the expression with multiple possible values, and return the corresponding results when matching

example

mysql> select user_id, case user_id when 1 then 'user_id = 1' when 2 then 'user_id = 2' else 'user_id not exist' end test_case from test;
+---------+-------------+
| user_id | test_case |
+---------+-------------+
| 1 | user_id = 1 |
| 2 | user_id = 2 |
+---------+-------------+

mysql> select user_id, case when user_id = 1 then 'user_id = 1' when user_id = 2 then 'user_id = 2' else 'user_id not exist' end test_case from test;
+---------+-------------+
| user_id | test_case |
+---------+-------------+
| 1 | user_id = 1 |
| 2 | user_id = 2 |
+---------+-------------+

keywords

CASE