mysql stored procedure select and update selected - mysql

Question

i am trying to write a stored procedure for mysql, and basicly, it will select one id, and update selected id's operationdate.
DELIMITER //
CREATE PROCEDURE getID(
IN proc_intervaldate datetime
)
BEGIN
DECLARE RUserID BIGINT;
SELECT
UserID
INTO RUserID
FROM Tasks
WHERE OperationDate < proc_intervaldate
LIMIT 1 ;
UPDATE Tasks SET OperationDate = now() WHERE UserID = RUserID;
SELECT RUserID ;
END //
DELIMITER ;
but when i use this, procedure, it will return UserID but not update, if i comment
SELECT RUserID
then, it updates, but no data returns.

Answer 1

when I use this, procedure, it will return UserID but not update, if I comment 'SELECT RUserID;' then, it updates, but no data returns.
You can change definition of stored procedure to use an OUT parameter rather than just IN. With that, you can just capture the OUT value on the same OUT parameter, in your scripting language. Meaning you need not execute:
SELECT RUserID ;
in your stored procedure.
Change your SP definition as below:
DELIMITER //
CREATE PROCEDURE getID( IN proc_intervaldate datetime, OUT RUserID bigint )
BEGIN
SELECT
UserID INTO RUserID
FROM Tasks
WHERE
OperationDate < proc_intervaldate
LIMIT 1 ;
UPDATE Tasks SET OperationDate = now() WHERE UserID = RUserID;
END;
//
DELIMITER ;
You can call this stored procedure like, for example, at MySQL console:
SET #RUserID := 0;
CALL getID( now(), #RUserID );
SELECT #RUserID;
Refer to:
MySQL: CALL procedure syntax
To get back a value from a procedure using an OUT or INOUT parameter,
pass the parameter by means of a user variable, and then check the
value of the variable after the procedure returns.