Functionality added or changed:
            OPTIMIZE TABLE will for MyISAM tables
            treat all NULL values as different when
            calculating cardinality. This helps in optimising joins
            between tables where one of the tables has a lot of
            NULL values in a indexed column:
SELECT * from t1,t2 where t1.a=t2.key_with_a_lot_of_null;
            Added join operator FORCE INDEX
            (key_list). This acts likes USE INDEX
            (key_list) but with the addition that a table scan
            is assumed to be VERY expensive. One bad thing with this is
            that it makes FORCE a reserved word.
          
Reset internal row buffer in MyISAM after each query. This will reduce memory in the case you have a lot of big blobs in a table.
Bugs fixed:
A security patch in 4.0.8 causes the mysqld server to die if the remote hostname can't be resolved. This is now fixed.
            Fixed crash when replication big LOAD DATA
            INFILE statement that caused log rotation.
          
This is a translation of the MySQL Reference Manual that can be found at dev.mysql.com. The original Reference Manual is in English, and this translation is not necessarily as up to date as the English version.

