查看mysql语句运行时间的2种方法

查看mysql语句运行时间的2种方法

网站运行很慢的时候，我就特别起知道为什么这么慢，所以我查啊查,数据库绝对是很重要的一部分，里面运行的sql是绝对不能放过的。平时做项目的时候，我也会注意sql语句的书写，写出一些高效的sql来，所以我会经常测试自己写的sql语句。我把我知道的二个方法，总结一下发出来。

一，show profiles 之类的语句来查看

1，查一下profile是不是打开了，默认是不打开的。

mysql> show profiles; Empty set (0.02 sec)  mysql> show variables like "%pro%"; +---------------------------+-------+ | Variable_name             | Value | +---------------------------+-------+ | profiling                 | OFF   | | profiling_history_size    | 15    | | protocol_version          | 10    | | slave_compressed_protocol | OFF   | +---------------------------+-------+ 4 rows in set (0.00 sec)

我查看一下profiles里面没有东西，所以公司的电脑里面profile是没有打开的，我查看了一下mysql变量，果然是OFF的。

2，开启profile，然后测试

开启profile

mysql> set profiling=1; Query OK, 0 rows affected (0.00 sec)

测试如下：

mysql> show tables; +----------------+ | Tables_in_test | +----------------+ | aa             | | bb             | | comment        | | string_test    | | user           | +----------------+ 5 rows in set (0.00 sec)  mysql> select * from aa; +----+------+------------+------+ | id | name | nname      | sex  | +----+------+------------+------+ |  2 | tank | bbbb,4bbbb | NULL | |  3 | zhang| 3,c,u      | NULL | +----+------+------------+------+ 2 rows in set (0.00 sec)  mysql> update aa set name='d'; Query OK, 2 rows affected (0.00 sec) Rows matched: 2  Changed: 2  Warnings: 0  mysql> delete from bb; Query OK, 2 rows affected (0.00 sec)  mysql> show profiles; +----------+------------+------------------------+ | Query_ID | Duration   | Query                  | +----------+------------+------------------------+ |        1 | 0.00054775 | show tables            | |        2 | 0.00022400 | select * from aa       | |        3 | 0.00026275 | update aa set name='d' | |        4 | 0.00043000 | delete from bb         | +----------+------------+------------------------+ 4 rows in set (0.00 sec)  mysql> show profile; +----------------------+-----------+ | Status               | Duration  | +----------------------+-----------+ | (initialization)     | 0.0000247 | | checking permissions | 0.0000077 | | Opening tables       | 0.0000099 | | System lock          | 0.000004  | | Table lock           | 0.000005  | | init                 | 0.0003057 | | query end            | 0.0000062 | | freeing items        | 0.000057  | | closing tables       | 0.000008  | | logging slow query   | 0.0000015 | +----------------------+-----------+ 10 rows in set (0.00 sec)  mysql> show profile for query 1; +----------------------+-----------+ | Status               | Duration  | +----------------------+-----------+ | (initialization)     | 0.000028  | | checking permissions | 0.000007  | | Opening tables       | 0.0000939 | | System lock          | 0.0000017 | | Table lock           | 0.0000055 | | init                 | 0.000009  | | optimizing           | 0.0000027 | | statistics           | 0.0000085 | | preparing            | 0.0000065 | | executing            | 0.000004  | | checking permissions | 0.000258  | | Sending data         | 0.000049  | | end                  | 0.0000037 | | query end            | 0.0000027 | | freeing items        | 0.0000307 | | closing tables       | 0.0000032 | | removing tmp table   | 0.0000275 | | closing tables       | 0.0000037 | | logging slow query   | 0.000002  | +----------------------+-----------+ 19 rows in set (0.00 sec)  mysql> show profile for query 3; +----------------------+-----------+ | Status               | Duration  | +----------------------+-----------+ | (initialization)     | 0.0000475 | | checking permissions | 0.0000077 | | Opening tables       | 0.000026  | | System lock          | 0.0000042 | | Table lock           | 0.0000045 | | init                 | 0.0000205 | | Updating             | 0.0000787 | | end                  | 0.0000567 | | query end            | 0.000004  | | freeing items        | 0.0000067 | | closing tables       | 0.000004  | | logging slow query   | 0.000002  | +----------------------+-----------+ 12 rows in set (0.00 sec)

二，timestampdiff来查看测试时间

mysql> set @d=now(); Query OK, 0 rows affected (0.00 sec)  mysql> select * from comment; +------+-----+------+------------+---------------------+ | c_id | mid | name | content    | datetime            | +------+-----+------+------------+---------------------+ |    1 |   1 | ??   | 2222222211 | 2010-05-12 00:00:00 | |    2 |   1 | ??   | ????(??)   | 2010-05-13 00:00:00 | |    3 |   2 | tank | ??????     | 0000-00-00 00:00:00 | +------+-----+------+------------+---------------------+ 3 rows in set (0.00 sec)  mysql> select timestampdiff(second,@d,now()); +--------------------------------+ | timestampdiff(second,@d,now()) | +--------------------------------+ |                              0 | +--------------------------------+ 1 row in set (0.00 sec)

这种方法有一点要注意，就是三条sql语句要尽量连一起执行，不然误差太大，根本不准

set @d=now(); select * from comment; select timestampdiff(second,@d,now());

如果是用命令行来执行的话，有一点要注意，就是在select timestampdiff(second,@d,now());后面，一定要多copy一个空行，不然最后一个sql要你自己按回车执行，这样就不准了。

其实我觉得吧，真正要我们关心的是，那些查询慢的sql,因为真正影响速度的是他们，关于慢查询的东西，有空写一下。