Question

I am in the process of converting a SQL Server 2005 database to MySQL and having problems with a Stored procedure. I’m new to MySQL stored procedures so I’m sure it is a problem with my conversion but I’m not seeing it.

The stored procedure is supposed to generate a temporary table which is used to populate a Data Grid View in a vb.net application. However, I’m getting the error “Data No Data – Zero rows fetched, selected or processed.”. Seems simple enough but the select procedure in the stored procedure will get data if I just run it as a query which is why I don’t understand why the error.

I’m really hoping someone can tell me why because I have several hundred stored procedures to convert and I’m having this problem on the very first one.

Here’s the Stored Procedure:

DELIMITER $$

DROP PROCEDURE IF EXISTS `usp_get_unassigned_media`$$

CREATE DEFINER=`showxx`@`67.111.11.110` PROCEDURE `usp_get_unassigned_media`()
BEGIN
    /* GET CURSOR WITH LOCAL LOCATIONS */
    DECLARE intKey INT; 
    DECLARE dteDateInserted DATETIME;
    DECLARE vchIdField VARCHAR(200); 
    DECLARE vchValueField VARCHAR(200); 
    DECLARE intLastKey INT;


/*TAKE OUT SPECIFIC PLAYLIST ITEMS IF TOO SLOW*/
DECLARE csrMediaToBeAssigned CURSOR FOR
SELECT
  `media`.`key`             AS `key`,
  `media`.`date_inserted`   AS `date_inserted`,
  `media_detail_types`.`id` AS `id`,
  `media_details`.`value`   AS `value`
FROM (`media`
   LEFT JOIN (`media_detail_types`
          JOIN `media_details`
        ON ((`media_detail_types`.`key` = `media_details`.`detail_key`)))
     ON ((`media_details`.`media_key` = `media`.`key`)))

WHERE ((`media`.`is_assigned` = 0)
       AND ((`media_detail_types`.`id` = 'Volume Name')
         OR (`media_detail_types`.`id` = 'Drive Id')))
ORDER BY `media`.`key`,`media`.`date_inserted`,`media_detail_types`.`id`;

OPEN csrMediaToBeAssigned;

DROP TEMPORARY TABLE IF EXISTS temp_unassigned_media;
CREATE TEMPORARY TABLE temp_unnassigned_media 
    (temp_key INT, DateInserted DATETIME, IdField VARCHAR(200), ValueField VARCHAR (200)) 
    ENGINE=MEMORY;
SET intLastKey = 0;
/*--GET FIRST RECORD */

FETCH FROM csrMediaToBeAssigned
    INTO intKey, dteDateInserted, vchIdField, vchValueField;
/*--LOOP THROUGH CURSOR */
WHILE intLastKey = 0 DO
    /*--DATA SHOULD BE IN DRIVE ID THEN VOLUME NAME */

    INSERT INTO  temp_unnassigned_media
        VALUES (intKey, dteDateInserted, vchValueField, '');
    FETCH NEXT FROM csrMediaToBeAssigned
        INTO intKey, dteDateInserted, vchIdField, vchValueField;

    UPDATE temp_unnassigned_media
        SET IdField = vchValueField
        WHERE temp_key = temp_key;
    FETCH NEXT FROM csrMediaToBeAssigned
        INTO intKey, dteDateInserted, vchIdField, vchValueField;

END WHILE;
SELECT * 
    FROM temp_unnassigned_media 
    ORDER BY date_inserted; 
CLOSE csrMediaToBeAssigned;     
/*DEALLOCATE csrMediaToBeAssigned   */
/*DROP TABLE #temp_unnassigned_media    */

END$$

DELIMITER ;

Answer 1

You never hit a condition where that WHILE loop will exit; you initialize intLastKey variable, but it never changes, so you fetch through the entire resultset. The exception is thrown when you fetch again, after the last record.

The normative pattern is to declare a CONTINUE HANDLER, which MySQL will execute when the NOT FOUND condition is triggered. The handler is normally used to set a variable, which you can then test, so you know when to exit the loop.

In your case, it looks like just adding this line, after your DECLARE CURSOR statement and before the OPEN statement, would be sufficient:

DECLARE CONTINUE HANDLER FOR NOT FOUND SET intLastKey = 1;