标签：style blog http ar color os sp on div
mysql> explain select customer_id,first_name,last_name from customer; +----+-------------+----------+------+---------------+------+---------+------+------+-------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+----------+------+---------------+------+---------+------+------+-------+ | 1 | SIMPLE | customer | ALL | NULL | NULL | NULL | NULL | 599 | NULL | +----+-------------+----------+------+---------------+------+---------+------+------+-------+ 1 row in set (0.00 sec)
返回各列的含义
extra列需要注意的返回值
Using filesort:看到这个的时候，查询就需要优化了
Using temporary 看到这个的时候，也需要优化，
http://www.imooc.com/video/3710
笔记
mysql> explain select max(payment_date) from payment\G *************************** 1. row *************************** id: 1 select_type: SIMPLE table: payment type: ALL possible_keys: NULL key: NULL key_len: NULL ref: NULL rows: 16086 Extra: NULL 1 row in set (0.00 sec) mysql>
标签：style blog http ar color os sp on div
原文地址：http://www.cnblogs.com/walter371/p/4170700.html
