Currently we may right a IF block like this:
IF boolean THEN
statements;
ELSE
IF boolean THEN
statements;
ELSE
statements;
END IF;
END IF;
However it is not desired for several cases. Then a better approach would be use something close to the usual switch
statements.
Related threads:
In order to mimic a switch statement, put the switch value directly after "CASE" before the "WHEN". Every when statement will check to see if it's value equals the CASE value.
Example using the specialized case statement to return hex color values for color words:
DO $$
DECLARE
test_color varchar;
hex_color varchar;
BEGIN
test_color := 'blue';
hex_color :=
CASE test_color
WHEN 'red' THEN
'#FF0000'
WHEN 'blue' THEN
'#0000FF'
WHEN 'yellow' THEN
'#FFFF00'
ELSE --we do not use that color, replace with white
'#FFFFFF'
END;
END $$
I'm not able to test the anonymous block on my computer so here's a straight SQL statement I've tested to work which can be used in an anonymous block:
SELECT
CASE 'blue'
WHEN 'red' THEN
'#FF0000'
WHEN 'blue' THEN
'#0000FF'
WHEN 'yellow' THEN
'#FFFF00'
ELSE --we do not use that color, replace with white
'#FFFFFF'
END;
The basic/base structure for the PL/pgSQL CASE with anonymous code block procedure block is:
DO $$ BEGIN
CASE
WHEN boolean-expression THEN
statements;
WHEN boolean-expression THEN
statements;
...
ELSE
statements;
END CASE;
END $$;
References:
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.