SQL error when trying to create new trigger

Question

And when I try to create a trigger:

CREATE TRIGGER ctg_el_del 
AFTER DELETE ON ctg
FOR EACH ROW
BEGIN
DELETE FROM ctg
       where ctg.id_ctg = old.lft
                  


        

Answer 1

STEP 1 : You need to Create function that returns type Trigger in that function you should mention the SQL Operation like below:

CREATE FUNCTION trigger_function() RETURNS TRIGGER AS $$
BEGIN
    DELETE FROM ctg 
    WHERE ctg.id_ctg = old.lft
    AND   ctg.id_ctg = old.rgt;
END
$$
LANGUAGE plpgsql;

STEP 2 : And then create the trigger on the table to call after delete like this:

CREATE TRIGGER ctg_el_del 
AFTER DELETE ON ctg
FOR EACH ROW
EXECUTE PROCEDURE trigger_function();