Question

I am working on a project and would like a notification each time a new record is added to a specific table in a MySQL DB. I would like a small popup to be displayed each time a new record is added, but without refreshing the page. I heard AJAX was the way to go, but am not very familiar with it.

Answer 1

Nope it won’t. The database won’t tell you when a record is inserted. You can use AJAX to send a request to the server. Then, that server can query for changes. It can send a response indicating whether there is a change. Then, the AJAX request’s response handler can show a message accordingly.

But implementing this will cause quite a load on both the webserver and the database server. So if you do this, choose the timing wisely. Don’t execute this procedure 10 times a second or you’ll kill your server as soon as you hit a 100 visitors.

To solve your problem, break it up in two pieces:
1. Get the actual AJAX request to work. Let the server return dummy values and try to handle them correctly. Hint: Use JQuery.ajax (or even JQuery.get) to ease your life.
2. Get the server to query for changes. If you want to monitor a single table this can easily be done. Add a timestamp column to the table if you don’t already have one. You can configure it so that it will be updated each time the table is updates. Then, query for the highest timestamp. Don’t forget to add an index to that column!

You can experiment with other solutions too. Add a trigger that alters a date/time in a different table. That way, the polling only needs to query that single column instead of the ‘max’ query.

To handle the change correctly, I think its best to let Javascript hold on to the last timestamp. Send the timestamp back in the response. Javascript can compare the timestamp to the last timestamp and show a message if needed. This way, you won’t need to keep the timestamps in the session.