Question

I have imported an excel document into MySQL to tidy up and make better use of the data but I am having problems running an update.

All tables used as examples below;

Tables
asset_register
phone
sim
team

The asset_register contains the following cols;

id INT,
serialNo VARCHAR,
simNo INT,
team VARCHAR

The problem is that I want to create a team table and the reference the teamId in the asset_register table.

Does that make sense? Instead of storing the actual team name i want a foreign key to the teams table.

The problem lies in updating all the data in the asset_register table which was imported from excel. There are nearly the same no of teams as users (~500) and I need to write a query or Stored Procedure to update all of them.

I thought that a stored procedure would be the way to go. So far i have the following but it updated the value of team to ‘NULL’ instead of the teamId.

    DELIMITER //
    DROP PROCEDURE `updateCrews`//
    CREATE DEFINER=`root`@`localhost` PROCEDURE `updateCrews`()

    BEGIN

DECLARE rowCount INT;
DECLARE crewNameFromRegister VARCHAR(7);
DECLARE currentRow INT;
DECLARE newCrewdata VARCHAR(7);

SET rowCount=(SELECT COUNT(*) FROM asset_register);
SET currentRow = 1;

myUpdateLoop: WHILE (currentRow < rowCount) DO

    SET crewNameFromRegister = (SELECT crewID FROM asset_register WHERE id = currentRow);   
    SET newCrewData = (SELECT id FROM crews WHERE crewName = crewNameFromRegister);
    UPDATE asset_register SET crewID = newCrewData;

    SET currentRow = currentRow + 1;

END WHILE myUpdateLoop;

    END//

    DELIMITER ;

Any help would be greatly appreciated, there is probably a better way to do this and a nudge in the right direction would be great.

Answer 1

If I good understand your question I suggest you to use a mutli table update syntax describe in mysql manual in this article : MutliTableUpdate. You try to change a string key by an id, be carreful of data type / conversion.

The idea should be:

UPDATE asset_register, crews
SET    asset_register.crewID = crews.id
WHERE  crews.crewName = asset_register.crewID 

But it could be safer if you use an other column column to do it and check the intermediate result.

On your first example:

id INT,
serialNo VARCHAR,
simNo INT,
team VARCHAR

you can add a teamID column, do the update and rename your column