Question

Howdie,

I’m trying writing a system that makes predictions about its users based on a test. For part of this I only want the database to store the most recent 500 values.

The current fields I am storing are

ID (Auto increment)
USERID (the users unique ID)
SCORE(an integer)

In an ideal world I would Like the system to drop the oldest row when a unique user gets over 500 records in the database. Is there an easy way to automate this in PHP without making the code really heavy?

Answer 1

You’ll have to store a date/time field so you can determine what’s over 1 month old, then it becomes as simple as:

DELETE FROM yourtable
WHERE timestampfield > (NOW() - INTERVAL 1 MONTH)

If you’re not going to have any ‘gaps’ in the auto_incremented ID, you could do a very simple (and very failure prone):

INSERT INTO ....  <--add new record

DELETE FROM yourtable WHERE (id < (INSERT_ID() - 500))

but this would be very unreliable.