Question

I have a trigger:

CREATE TRIGGER BEFORE_DELETE_ON_SENTIERO__HA__TAPPA
BEFORE DELETE ON SENTIERO__HA__TAPPA
FOR EACH ROW 
BEGIN

DECLARE temp_prima_tappa INTEGER;
DECLARE temp_ultima_tappa INTEGER;

-- NOW THIS QUERY WILL FAIL;   it checks if the record that has to be deleted is in the table
IF NOT EXISTS ( SELECT *
                FROM SENTIERO__HA__TAPPA as sht
                WHERE OLD.IDsentiero=sht.IDsentiero and OLD.IDtappa=sht.IDtappa) THEN

                        SIGNAL SQLSTATE '45000'
                        SET MESSAGE_TEXT = 'DELETE: La tappa indicata non è nel sentiero; impossibile elimnarla';

END IF;

IDsentiero and IDtappa are PK of of their relative tables: IDsentiero for SENTIERO, IDtappa for TAPPA.

The problem is that the DELETE QUERY doesn’t reply me with that error message; simply it let runs DELETE QUERY, although it cannot delete anything, because that record doesn’t exist in the table.

The problem is that query.. i’m sure but i cannot find the bug.

Answer 1

Something like this should work:

declare recsexist int;
set recsexist = 0;  

SELECT 1 INTO recsexist 
FROM SENTIERO__HA__TAPPA as sht
WHERE OLD.IDsentiero=sht.IDsentiero and OLD.IDtappa=sht.IDtappa;

IF (recsexist > 0) THEN
     ...

END IF;