Fixed in MySQL 4.1.10: Using HAVING, you can get a crash or wrong result if you use an alias to a RAND() function. This will not be fixed in 4.0 because the fix may break compatability with some applications.

Fixed in MySQL 4.1.1: In a UNION, the first SELECT determines the type, max_length, and NULL properties for the resulting columns.

Fixed in MySQL 4.1: In DELETE with many tables, you can't refer to tables to be deleted through an alias.

Fixed in MySQL 4.1.2: You cannot mix UNION ALL and UNION DISTINCT in the same query. If you use ALL for one UNION, it is used for all of them.

FLUSH TABLES WITH READ LOCK does not block CREATE TABLE, which may cause a problem with the binary log position when doing a full backup of tables and the binary log.

Fixed in MySQL 4.1.8: mysqldump --single-transaction --master-data behaved like mysqldump --master-data, so the dump was a blocking one.

When using the RPAD() function (or any function adding spaces to the right) in a query that had to be resolved by using a temporary table, all resulting strings had rightmost spaces removed (that is, RPAD() did not work).