MySQL Newsletter Optimizing OR queries with MySQL 4.0

In the easiest case, when you do not need to perform any sort or group by on query result you just can rewrite it using UNION

SELECT * from articles where author="Monty"
UNION ALL
SELECT * from articles where rating=5 and author!="Monty"

Note where clause in the second query. Without it you may get the duplicate rows in result if they match both ORed clauses.

If you need to have more complex query, you will likely to need to create temporary table:

CREATE TEMPORARY TABLE result type=heap SELECT * from articles where author="Monty"
UNION ALL
SELECT * from articles where rating=5 and author!="Monty"

Note, creation of temporary heap (in memory) table is quite fast and adds almost no performance overhead.

Now you may run the group by/order by part of the query

select * from result order by author,rating

You should also drop temporary table after use, but if you forget to do so, it will be automatically droped when connection is closed.