MySQL优化 – EXPLAIN

EXPLAIN是我们最常用的SQL分析工具,在使用工具之前我们需要先了解下工具中每一项代表的含义,如下是EXPLAIN中的所有列: mysql> explain select * from user u1 left join user u2 on u1.id=u2.id where u1.name='wyh'; +----+-------------+-------+------------+--------+------------------+------------------+---------+----------------+------+----------+-------+ |