同大多数关系型数据库一样，日志文件是MySQL数据库的重要组成部分。MySQL有几种不同的日志文件，通常包括错误日志文件，二进制日志，通用日志，慢查询日志，等等。这些日志可以帮助我们定位mysqld内部发生的事件，数据库性能故障，记录数据的变更历史，用户恢复数据库等等。本文主要描述通用查询日志。

1、MySQL日志文件系统的组成 

2、通用查询日志 

3、通用查询日志的系统变量 

4、通用查询日志的备份

5、演示通用查询日志的使用

a、启用通用查询日志
--演示环境
root@localhost[(none)]> show variables like '%version%';
+-------------------------+------------------------------+
| Variable_name           | Value                        |
+-------------------------+------------------------------+
| innodb_version          | 5.5.39                       |
| protocol_version        | 10                           |
| slave_type_conversions  |                              |
| version                 | 5.5.39-log                   |
| version_comment         | MySQL Community Server (GPL) |
| version_compile_machine | x86_64                       |
| version_compile_os      | Linux                        |
+-------------------------+------------------------------+

--查看系统变量
root@localhost[(none)]> show variables like '%general%';
+------------------+----------------------------+
| Variable_name    | Value                      |
+------------------+----------------------------+
| general_log      | OFF                        |
| general_log_file | /var/lib/mysql/suse11b.log |
+------------------+----------------------------+

--查看当前的通用日志，显示无日志文件
root@localhost[(none)]> system ls /var/lib/mysql/suse11b.log 
ls: cannot access /var/lib/mysql/suse11b.log: No such file or directory
--设置变量general_log以开启通用查询日志
root@localhost[(none)]> set @@global.general_log=1;
Query OK, 0 rows affected (0.00 sec)

--再次查看通用日志文件已存在
root@localhost[(none)]> system ls /var/lib/mysql/suse11b.log 
/var/lib/mysql/suse11b.log
root@localhost[(none)]> select * from tempdb.tb1;  --执行查询
+------+------+
| id   | val  |
+------+------+
|    1 | jack |
+------+------+

--查看通用日志文件内容
root@localhost[(none)]> system more /var/lib/mysql/suse11b.log
/usr/sbin/mysqld, Version: 5.5.39-log (MySQL Community Server (GPL)). started with:
Tcp port: 3306  Unix socket: /var/lib/mysql/mysql.sock
Time                 Id Command    Argument
141003 16:18:12     4 Query     show variables like '%general%'
141003 16:18:55     4 Query     select * from tempdb.tb1


b、更改通用查询日志位置
root@localhost[(none)]> exit
Bye
suse11b:~ # service mysql stop
Shutting down MySQL...                                          done
suse11b:~ # mysqld --general_log_file=/tmp/suse11b.log --user=mysql &
[1] 47009
suse11b:~ # ps -ef|grep mysql|grep -v grep
mysql    47009 44514  1 16:22 pts/0    00:00:00 mysqld --general_log_file=/tmp/suse11b.log --user=mysql
root     47053 44514  0 16:22 pts/0    00:00:00 grep mysql
suse11b:~ # mysql
root@localhost[(none)]> system ls /tmp/suse11b.log
ls: cannot access /tmp/suse11b.log: No such file or directory
root@localhost[(none)]> show variables like '%gener%';
+------------------+------------------+
| Variable_name    | Value            |
+------------------+------------------+
| general_log      | OFF              |
| general_log_file | /tmp/suse11b.log |
+------------------+------------------+

root@localhost[(none)]> set global general_log=on;
Query OK, 0 rows affected (0.01 sec)

--此时从系统变量看出，通用日志已经到/tmp目录下
root@localhost[(none)]> show variables like '%gener%';
+------------------+------------------+
| Variable_name    | Value            |
+------------------+------------------+
| general_log      | ON               |
| general_log_file | /tmp/suse11b.log |
+------------------+------------------+

--发布查询
root@localhost[(none)]> select count(*) from tempdb.tb1;
+----------+
| count(*) |
+----------+
|        1 |
+----------+

--查看通用日志文件内容
root@localhost[(none)]> system more /tmp/suse11b.log
mysqld, Version: 5.5.39-log (MySQL Community Server (GPL)). started with:
Tcp port: 3306  Unix socket: /var/lib/mysql/mysql.sock
Time                 Id Command    Argument
141003 16:30:03     1 Query     show variables like '%gener%'
141003 16:30:09     1 Query     select count(*) from tempdb.tb1


c、通用查询日志输出方式
--可以输出为文件，表以及不输出，即TABLE，FILE，NONE
--系统变量log_output
root@localhost[(none)]> show variables like 'log_output';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log_output    | FILE  |
+---------------+-------+

--下面修改为输出为表方式
root@localhost[(none)]> set global log_output='TABLE';
Query OK, 0 rows affected (0.00 sec)

root@localhost[(none)]> show variables like 'log_output';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log_output    | TABLE |
+---------------+-------+

--发布查询
root@localhost[(none)]> select * from tempdb.tb1;
+------+------+
| id   | val  |
+------+------+
|    1 | jack |
+------+------+

--Author: Leshami
--Blog  : http://blog.csdn.net/leshami

root@localhost[(none)]> system more /tmp/suse11b.log
mysqld, Version: 5.5.39-log (MySQL Community Server (GPL)). started with:
Tcp port: 3306  Unix socket: /var/lib/mysql/mysql.sock
Time                 Id Command    Argument
141003 16:30:03     1 Query     show variables like '%gener%'
141003 16:30:09     1 Query     select count(*) from tempdb.tb1
141003 16:31:00     1 Query     show variables like 'log_output'
141003 17:00:48     1 Query     set global log_output='TABLE'  #通用查询日志输出到文件仅仅记录到全局变量的修改

--mysql.general_log记录了通用查询日志的信息
root@localhost[(none)]> desc mysql.general_log;
+--------------+------------------+------+-----+-------------------+-----------------------------+
| Field        | Type             | Null | Key | Default           | Extra                       |
+--------------+------------------+------+-----+-------------------+-----------------------------+
| event_time   | timestamp        | NO   |     | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
| user_host    | mediumtext       | NO   |     | NULL              |                             |
| thread_id    | int(11)          | NO   |     | NULL              |                             |
| server_id    | int(10) unsigned | NO   |     | NULL              |                             |
| command_type | varchar(64)      | NO   |     | NULL              |                             |
| argument     | mediumtext       | NO   |     | NULL              |                             |
+--------------+------------------+------+-----+-------------------+-----------------------------+

--从通用查询日志表里查看通用查询日志的内容
root@localhost[(none)]> select thread_id,command_type,argument from mysql.general_log; 
+-----------+--------------+---------------------------------------------------------------+
| thread_id | command_type | argument                                                      |
+-----------+--------------+---------------------------------------------------------------+
|         1 | Query        | show variables like 'log_output'                              |
|         1 | Query        | select * from tempdb.tb1                                      |
|         1 | Query        | desc mysql.general_log                                        |
|         1 | Query        | select thread_id,command_type,argument from mysql.general_log |
+-----------+--------------+---------------------------------------------------------------+

root@localhost[(none)]> show variables like 'log_output';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| log_output    | TABLE |
+---------------+-------+

--使用FILE,TABLE 2者混合输出通用日志
root@localhost[(none)]> set global log_output='file,table';
Query OK, 0 rows affected (0.00 sec)

root@localhost[(none)]> select @@global.log_output;
+---------------------+
| @@global.log_output |
+---------------------+
| FILE,TABLE          |
+---------------------+

root@localhost[(none)]> insert into tempdb.tb1 values(2,'robinson');
Query OK, 1 row affected (0.06 sec)

root@localhost[(none)]> commit;
Query OK, 0 rows affected (0.01 sec)

--验证结果，表和文件里边存在通用的日志记录
root@localhost[(none)]> system tail /tmp/suse11b.log|grep robinson
141003 17:41:54     2 Query     insert into tempdb.tb1 values(2,'robinson')
root@localhost[(none)]> select thread_id,command_type,argument from mysql.general_log
    -> where argument like '%robinson%';
+-----------+--------------+------------------------------------------------------------------------+
| thread_id | command_type | argument                                                               |
+-----------+--------------+------------------------------------------------------------------------+
|         2 | Query        | insert into tempdb.tb1 values(2,'robinson')                            |
|         2 | Query        | select thread_id,command_type,argument from mysql.general_log          |
|           |              |    where argument like ''robinson''                                    | 
+-----------+--------------+------------------------------------------------------------------------+

d、关闭通用查询日志
--可以通过设置系统变量general_log来关闭通用查询日志，此时日志输出设置为FILE,TABLE
root@localhost[(none)]> show variables like 'log_output';
+---------------+------------+
| Variable_name | Value      |
+---------------+------------+
| log_output    | FILE,TABLE |
+---------------+------------+

root@localhost[(none)]> set global general_log=off;
Query OK, 0 rows affected (0.01 sec)

root@localhost[(none)]> show variables like '%gener%';
+------------------+------------------+
| Variable_name    | Value            |
+------------------+------------------+
| general_log      | OFF              |
| general_log_file | /tmp/suse11b.log |
+------------------+------------------+

root@localhost[(none)]> delete from tempdb.tb1 where id=2;
Query OK, 1 row affected (0.12 sec)

root@localhost[(none)]> commit;
Query OK, 0 rows affected (0.00 sec)

root@localhost[(none)]> system tail -n 1 /tmp/suse11b.log
141003 17:45:13     2 Query     set global general_log=off

root@localhost[(none)]> select thread_id,command_type,argument from mysql.general_log
    -> where argument like '%delete%';
Empty set (0.00 sec)

--从上面的演示可知，尽管我们设置了log_output为FILE,TABLE，但general_log为OFF，通用日志无任何记录产生

root@localhost[(none)]> set global log_output=none;
Query OK, 0 rows affected (0.00 sec)

root@localhost[(none)]> set global general_log=1;
Query OK, 0 rows affected (0.00 sec)

root@localhost[(none)]> truncate table tempdb.tb1;
Query OK, 0 rows affected (0.01 sec)

root@localhost[(none)]> system tail -n 1 /tmp/suse11b.log
Time                 Id Command    Argument

--通过上面的演示，在log_output=none,general_log=on的清下下无任何通用日志输出。