Postgres nested if requested

Question

Could you tell me why the following does not work in postgres sql ?:

See updated code below 

UPDATE:

I expect the request to return "0.30" as a float. This design is for testing purposes only, I have some complex queries that depend on this conditional structure ... BUt I do not know how to fix it ..

Result:

 ERROR: syntax error at or near "1" LINE 4: if 1=1 then 

UPDATE:

This construct appears in the function ... so I want to do the following:

 CREATE FUNCTION f_test(myvalue integer) RETURNS float AS $$ BEGIN select ( case (select '1') when '1' then if 1=1 then 0.30::float else 0.50::float end else 1.00::float end ); END; $$ LANGUAGE plpgsql; select f_test(1) as test; 

Error message see above.

Answer 1

There is no syntax IF expr THEN result ELSE result END for regular SQL queries in Postgres. Since there is no IF() function, as in MySQL, you should use CASE :

 select ( case (select '1') when '1' then case when 1=1 then 0.30::float else 0.50::float end else 1.00::float end ); 

Answer 2

I don’t know what you are trying to achieve with this function, but here is the working version.

 CREATE FUNCTION f_test(myvalue integer) RETURNS float AS $$ BEGIN IF myvalue = 1 THEN IF 1=1 THEN RETURN 0.30::FLOAT; ELSE RETURN 0.50::FLOAT; END IF; ELSE RETURN 1.0::FLOAT; END IF; END; 

The function returns 0.3 if the input value is 1, otherwise it will return 1. Edit: Note that the function is never returned by the function.