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I feel MySQL is not as good as MS SQL server is also because MySQL has more bugs. Depends on how you use MyQL the bugs may not border you. I have seen two major bugs in its 5.0.41 NT version that once made me that think that MySQL was only a toy.

One of the bugs I observed in that version was the number of concurrent connections it can support. I might be

the first one to report the bug on that version to MySQL. If you set innodb_buffer_pool_size to relatively large size, the number of concurrent connections could be down to 15. For a small innodb_buffer_pool_size the number of concurrent connection can be up to 60 something. This number of concurrent connections is not able to support high traffic internet application where hundreds of concurrent connections may be required. I remember I had to down grade MySQL to a lower version to get around this problem. Of course MySQL 6.0 is coming out. Most likely the problem was fixed in later release.

Another bug that I saw in both 5.0.41 and earlier version 5.0.36 is that MySQL has really bad performance with queries in Anti Semi join Syntax. A sample of anti semi join syntax is like this.

Select * from tableA a where a.id not in (select b.id from tableB b)

If the two tables are small tables you may not feel the problem. But if the two tables are big tables the slowness of the above query is very obvious even when both tables have proper index built. The way to around this is to rephrase the query in left join syntax.

Select * from tableA a left join tableB b on a.id=b.id where b.id is null

The query in left join syntax can be 100 times faster than the one in anti semi join.

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