I was surprised to find yesterday when using MySQL 5.1.26-rc with a client I’m recommending 5.1 to, some information not seen in the EXPLAIN plan before while reviewing SQL Statements.
Using join buffer
+----+-------------+-------+--------+---------------+--------------+---------+------------------------+-------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+---------------+--------------+---------+------------------------+-------+----------------------------------------------+ | 1 | SIMPLE | lr | ALL | NULL | NULL | NULL | NULL | 1084 | Using where; Using temporary; Using filesort | | 1 | SIMPLE | ca | ref | update_check | update_check | 4 | XXXXXXXXXXXXXXXXX | 4 | Using …[Read more]