[GENERAL] How to raise error from PostgreSql SQL statement if some condition is met

[Andrus]

I’m looking for a way to raise error from sql select if some condition is met.
Tried code below to got error shown in comment.
How to fix ?

Andrus

    CREATE OR REPLACE FUNCTION "exec"(text)
      RETURNS text AS
    $BODY$ 
        BEGIN 
          EXECUTE $1; 
          RETURN $1; 
        END; 
    $BODY$
      LANGUAGE plpgsql VOLATILE;
      
    -- ERROR:  syntax error at or near "raise"
    -- LINE 1: raise 'test' 
    
    select exec('raise ''test'' ') where true -- in real application true is 
replaced by some condition