sql - Query has no destination for result data, although it should -

here simplified version of function have:

create or replace function my_funct(user_id integer)   returns integer $body$ declare   my_var integer;  begin   //....................   if not exists (select * table1)     return 0;   end if;    my_var := (select count(*) table2     inner join ..............   );    return (select field1 table3) - my_var; end; $body$   language plpgsql volatile   cost 100; alter function my_funct(integer)   owner postgres; 

but call play framework, error:

[psqlexception: error: query has no destination result data  hint: if want discard results of select, use perform instead.  where: pl/pgsql function my_funct(integer)   @ sql statement] 

update:

 ------------------------------------------------    if not exists (select * table1)     select try_to_update_table1(user_id); -- cause. updates table1   end if;   if not exists (select * table1)     return 0;   end if;   ------------------------------------------------ 

the code display should work is. (i tested in 9.3 , does.)
error message unrelated , caused not in question. answer that:
error: query has no destination result data while using cursor

asides

(select field1 table3) without where condition doesn't make lot of sense, still work.

your original code:

if not exists (select * table1)    return 0; end if; 

is superior suggested alternative:

perform * table1; if not found    return null; end if; 

returning 0 or null question of requirements. there no "standard behavior".