Delete MySQL row where multiple indexes are the same, but keep the most recent

Question

Here is what my table looks like
=======================================
|| id | collection_id | product_id | price ||
=======================================
|| 1  |   1    |   1   | 2.50  ||
|| 2  |   1    |   1   | 2.60  ||
|| 3  |   1    |   1   | 2.40  ||
|| 4  |   2    |   1   | 2.50  ||
=======================================

Here is a rough outline of what I want to achieve; using some pseudo code.

What I want to do is DELETE FROM prices WHERE (collection_ id && product_ id are duplicated) AND WHERE (id < highest duplicated row)

SO what I want to do in plain English is delete rows where the id is equal to 1 & 2 but keep the row where the id is equal to 3 because this the newest.

Answer 1

A simple DELETE JOIN should do it; delete all rows where there exists at least one row with a matching collection_id and product_id and a greater value of id;

DELETE p1
FROM prices p1
JOIN prices p2
  ON p1.collection_id = p2.collection_id
 AND p1.product_id = p2.product_id
 AND p1.id < p2.id

An SQLfiddle to test with, and remember to always back up your data before running updates or deletes from random people on the Internet.