如果觉得explain的信息不够详细，可以同通过profiling命令得到更准确的SQL执行消耗系统资源的信息。

profiling默认是关闭的。可以通过以下语句查看 select @@profiling;

打开功能： mysql>set profiling=1; 执行需要测试的sql 语句：

开启后执行了sql语句 就可以通过show profiles;命令查看执行时间

SQL

mysql> show profiles;
+----------+------------+---------------------------+
| Query_ID | Duration   | Query                     |
+----------+------------+---------------------------+
|        1 | 0.00417000 | select * from user        |
|        2 | 0.00214700 | select count(*) from user |
+----------+------------+---------------------------+
2 rows in set, 1 warning (0.00 sec)

mysql> show profiles\G; 可以得到被执行的SQL语句的时间和ID

mysql>show profile for query 1; 得到对应SQL语句执行的详细信息

Bash

mysql> show profile for query 1;
+----------------------+----------+
| Status               | Duration |
+----------------------+----------+
| starting             | 0.001587 |
| checking permissions | 0.000351 |
| Opening tables       | 0.000015 |
| init                 | 0.000021 |
| System lock          | 0.000264 |
| optimizing           | 0.000014 |
| statistics           | 0.000014 |
| preparing            | 0.000012 |
| executing            | 0.000003 |
| Sending data         | 0.001485 |
| end                  | 0.000018 |
| query end            | 0.000120 |
| closing tables       | 0.000026 |
| freeing items        | 0.000157 |
| cleaning up          | 0.000083 |
+----------------------+----------+
15 rows in set, 1 warning (0.00 sec)