hge-blog-pg-triggers-trigger.sql

-- Create the function
CREATE FUNCTION insert_deposit()
  RETURNS trigger AS $BODY$
DECLARE active_account BOOLEAN;
BEGIN
 IF NEW."deposit_amount" <= 0 THEN
     RAISE EXCEPTION 'Deposit amount must be greater than 0';
 END IF;
 SELECT a.is_active INTO active_account FROM "account_savings" a WHERE a.account_no = NEW."account_no";
 IF active_account != TRUE THEN
     RAISE EXCEPTION 'Account must be active';
 END IF;
 RETURN NEW;
END;
$BODY$ LANGUAGE plpgsql;

--- Create the trigger with the above function
CREATE TRIGGER insert_deposit BEFORE INSERT OR UPDATE ON "deposit_activity" FOR EACH ROW EXECUTE PROCEDURE insert_deposit();