mysql中explain命令详解

模拟Mysql优化器是如何执行SQL查询语句的，从而知道Mysql是如何处理你的SQL语句的。分析你的查询语句或是表结构的性能瓶颈。

mysql> explain select * from tb_user;
+----+-------------+---------+------+---------------+------+---------+------+------+-------+
| id | select_type | table  | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+---------+------+---------------+------+---------+------+------+-------+
| 1 | SIMPLE   | tb_user | ALL | NULL     | NULL | NULL  | NULL |  1 | NULL |
+----+-------------+---------+------+---------------+------+---------+------+------+-------+