It's possible to modify the way in which MySQL interprets certain parts of SQL, useful when porting queries from other databases. For example, the option PIPES_AS_CONCAT will persuade it to accept || as a concatenation operator rather than as a synonym for OR (see also gotcha 1.12). In 4.1 this facility has been extended considerably.
After a long testing period MySQL 4.1 has finally been declared production ready and is available for download. Representing a further incremental step in MySQL's steady advancement towards fully-fledged RDBMS-dom, it provides several sorely-missed features including sub-SELECTs.
It looks like MySQL are moving their mailing lists to a forum-based solution, currently in beta-testing. Whether these will completely replace the lists, or provided an alternative web-based interface, isn't yet clear.
Having recently debugged a MySQL replication setup, I was having a hard time keeping track of which database was open in which mysql command line client, as since before the start of time the prompt has been a very terse mysql> , giving no visual clue to which database is currently the default.
Fortunately, beginning with release 4.0.2 MySQL now provides a little-known option to set the prompt in a manner similar to that used in UNIX shells.
While browsing the online documentation I came across this snippet:
From MySQL 4.1.0, the attribute SERIAL can be used as an alias for BIGINT UNSIGNED NOT NULL AUTO_INCREMENT UNIQUE. This is compatibility feature.