Question

I have two tables, a message table and a log table.

I want to return all rows in the message table that have been logged to a user and whose message # is greater than a passed parameter.

What I have is:

SELECT * FROM message WHERE id IN ( SELECT msg_id AS id FROM msg_log WHERE user_num='1000' AND msg_id >='1660192')

This query returns nothing, produces no errors, it simply times out… It doesn’t matter if it run from a PHP script or phpMyAdmin. In fact, if run from phpMyAdmin it doesn’t even show the query is running, but it doesn’t allow you to execute another query.

If I break out the IN select

SELECT msg_id AS id FROM msg_log WHERE user_num='1000' AND msg_id >='1660192')

This returns 0 records (as it should)

How do I fix this problem?

Answer 1

Try this:

SELECT message.* FROM message 
INNER JOIN msg_log 
    ON message.id = msg_log.msg_id
   AND msg_log.user_num = '1000' 
   AND msg_logmsg_id >= '1660192'

The INNER JOIN syntax should be faster than IN clause.
Naturally you could speed query up having

• message.id as INDEX or PRIMARY_KEY
• msg_log.id as INDEX and probably related to message.id with a FOREIGN_KEY