Features that MySQL Does Not Support
This section describes features that are found in some other databases that MySQL does not support. It covers what's missing, and it shows how to work around these omissions where possible. In general, features are missing from MySQL because they have negative performance implications. Several of the items in this list are on the developers' To Do list, for implementation as time permits, and assuming a way can be found to do so without sacrificing their primary goal of good performance.
Subselects. A subselect is a SELECT nested inside another SELECT, such as in the following query:
SELECT * FROM score WHERE event_id IN (SELECT event_id FROM event WHERE type = "T")
Subselects are scheduled to appear in ...