Question

I want to update a MySQL table with information from two other tables. I’ll set up a cron job, but I don’t know what PHP code to use.

Every time the cron job runs, I want the ‘VideoNumber’ column from the ‘Profiles’ table to be updated with the amount of videos they’ve uploaded to the site. Video information is stored in a table called ‘Videos’, and each video has an ‘OwnerID’ to identify the user who uploaded it. This corresponds to the ‘ID’ column in the ‘Profiles’ table.

I also wanted the ‘PhotoNumber’ column in the ‘Profiles’ table to be updated with the amount of photos the same user has uploaded – photo data is stored in the ‘Photos’ column.

Can anybody help?

Answer 1

You’re doing it wrong. Update values of those columns immediately after new video/photo is created/deleted. You can enclose everything within transaction to make sure that everything will be fine:

BEGIN TRANSACTION;
INSERT INTO videos VALUES (...);
UPDATE profiles SET videosCount = videosCount + 1 WHERE id = ?;
COMMIT;



BEGIN TRANSACTION;
DELETE FROM videos WHERE id = ?;
UPDATE profiles SET videosCount = videosCount - 1 WHERE id = ?;
COMMIT;

Do the same for photos.

You can even use triggers to make everything clearer (ie. let database handle increase/decrease count columns’ values)

DELIMITER \\
CREATE TRIGGER abc AFTER INSERT ON videos
FOR EACH ROW BEGIN
   UPDATE profiles SET videosCount = videosCount + 1 WHERE id = NEW.profile_id;
END\\

DELIMITER ;