[STORED]Verica del parametro

[lbottoni]

Ciao,
se qualcuno ha esperienza nelle stored potrebbe dirmi se una cosa del genere è possibile:

io ho questa stored procedure

DELIMITER $$

DROP PROCEDURE IF EXISTS `test` $$
CREATE DEFINER=`provuser`@`%` PROCEDURE `test`(IN p1 VARCHAR(50))
BEGIN
SELECT
SELF_SOAP_ACTION.id_InstanceName,
SELF_SOAP_ACTION.ItnServiceRequestId,
SELF_SOAP_ACTION.ItnServiceInstanceName,
SELF_SOAP_ACTION.time_firstrequest,
SELF_SOAP_ACTION.time_requestexpired,
SELF_SOAP_ACTION.isactive,
SELF_SOAP_ACTION.CorrelationID,
SELF_SOAP_ACTION.status_request
FROM
SELF_SOAP_ACTION
WHERE
SELF_SOAP_ACTION.ItnServiceRequestId = p1;
END $$

DELIMITER ;

vorrei controllare se p1 è nullo...ho provato con:

DELIMITER $$

DROP PROCEDURE IF EXISTS `test` $$
CREATE DEFINER=`provuser`@`%` PROCEDURE `test`(IN p1 VARCHAR(50))
BEGIN
IF ISNULL(p1) THEN
p1='%';
END IF

SELECT
SELF_SOAP_ACTION.id_InstanceName,
SELF_SOAP_ACTION.ItnServiceRequestId,
SELF_SOAP_ACTION.ItnServiceInstanceName,
SELF_SOAP_ACTION.time_firstrequest,
SELF_SOAP_ACTION.time_requestexpired,
SELF_SOAP_ACTION.isactive,
SELF_SOAP_ACTION.CorrelationID,
SELF_SOAP_ACTION.status_request
FROM
SELF_SOAP_ACTION
WHERE
SELF_SOAP_ACTION.ItnServiceRequestId = p1;
END $$

DELIMITER ;

ma va sempre in errore!!!