Syntax
------ 
CASE case_value
 WHEN when_value THEN statement_list
 [WHEN when_value THEN statement_list] ...
 [ELSE statement_list]
END CASE
 
Or:
 
CASE
 WHEN search_condition THEN statement_list
 [WHEN search_condition THEN statement_list] ...
 [ELSE statement_list] 
END CASE
 
Description
----------- 
The CASE statement for stored programs implements a complex
conditional
construct. If a search_condition evaluates to true, the
corresponding SQL
statement list is executed. If no search condition matches,
the statement list
in the ELSE clause is executed. Each statement_list consists
of one or
more statements.
 
If no when_value or search_condition matches the value
tested and the CASE
statement contains no ELSE clause, a Case not found for CASE
statement
error results.
 
Each statement_list consists of one or more statements; an
empty
statement_list is not allowed. To handle situations where no
value is
matched by any WHEN clause, use an ELSE containing an
empty BEGIN ... END block, as shown in this example:
 
DELIMITER |
CREATE PROCEDURE p()
BEGIN
 DECLARE v INT DEFAULT 1;
 
 CASE v
 WHEN 2 THEN SELECT v;
 
 WHEN 3 THEN SELECT 0;
 
 ELSE BEGIN END;
 
 END CASE;
 
END;
 
|
 
The indentation used here in the ELSE clause is for purposes
of clarity only,
and is not otherwise significant. See Delimiters in the
mysql client for more on the use of the delimiter command.
 
Note: The syntax of the CASE statement used inside stored
programs
differs slightly from that of the SQL CASE expression
described in
CASE OPERATOR.
The CASE statement cannot have an ELSE NULL clause, and it
is
terminated with END CASE instead of END.
 

 
 
 
 
 
 
 

URL: https://mariadb.com/kb/en/case-statement/