mos a écrit : > This should be so simple, yet I've struck out. > > I have 2 tables, each with a common column called "pid" which is an > integer and is a unique index. There are approx 18 million rows in each > table, and one of the tables has approx 5000 fewer rows than the other > table. So it should be a piece of cake finding the missing rows right? > > Well I did a > > select * from t1 left join t2 on t1.pid=t2.pid where t2.pid is null > select * from t2 left join t1 on t2.pid=t1.pid where t1.pid is null > > and both queries return a null set. I then checked both tables and none > of them have pid as null. > I then counted the number of non-unique pid's and there aren't any (of > course with a unique index I didn't think there would be) > > Ok, so there are no rows in t1 that aren't in t2, and vice versa. > There are no duplicate sid values and no empty sid values. > I physically counted the rows in each table and they are indeed off by > around 5000 rows. > I checked the tables for consistency and they passed. > > How can anyone explain this? How do I find the missing rows? > TIA > > Mike > >
The 2 queries you paste seemed correct and should output the result unless there is something really strange happening. If you are using a version that support subquery you could try select * from t1 where id not in (select id from t2); Not sure which exactly is suppose to be faster but it's worth a try! Is it possible that you are hitting some kind of limit on maximum join number in your server ? I'm not even sure if a limit of that kind exists (Just putting my tought on the table) -- Mathieu Bruneau aka ROunofF === GPG keys available @ http://rounoff.darktech.org -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]