Prepared statement returning zero results

Question

I am attempting to execute the following prepared statement:

PREPARE stmt FROM 'SELECT * FROM Inventory I WHERE I.ParentId = ?';
EXECUTE stmt USING @parentId;

DEALLOCATE PREPARE stmt;

When I execute this statement, it returns the column headers with no rows. It should return 6 rows.

If I execute this same statement as a normal SQL statement without the PREPARE and EXECUTE statement, I get results, eg

SELECT * FROM Inventory I WHERE I.ParentId = parentId;

Results are returned. What am I doing wrong? Is there some kind of casting going on that is making my statement invalidate?

Update, parentId is passed in as a parameter, eg

CREATE DEFINER=`george`@`%` PROCEDURE `ListInventoryByParentId`(IN parentId INT)

Answer 1

User variable @parentId and procedure argument parentID are independent. You need to set your user variable to procedure argument before executing statement.

SET @parentID = parentId;