开启通用查询日志
因为为了性能考虑，一般通用查询日志general log不会开启。slow log可以定位一些有性能问题的sql，而general log会记录所有的sql。
mysql5.0版本，如果要开启slow log、general log，需要重启，从mysql5.1.6版开始，general query log和slow query log开始支持写到文件或者数据库表两种方式，并且日志的开启，输出方式的修改，都可以在global级别动态修改。
mysql>select version();
+————+ | version() | +————+ | 5.1.37-log | +————+ 1 row in set (0.02 sec)
设置日志输出方式为文件（如果设置log_output=table的话，则日志结果会记录到名为gengera_log的表中，这表的默认引擎都是csv）：
mysql>set global log_output=file;
query ok, 0 rows affected (0.00 sec)
设置general log的日志文件路径：
mysql>set global general_log_file='/tmp/general.log';
query ok, 0 rows affected (0.00 sec)
开启general log：
mysql>set global general_log=on;
query ok, 0 rows affected (0.02 sec)
过一段时间后，关闭general log：
mysql>set global general_log=off;
query ok, 0 rows affected (0.02 sec)
通用查询日志的系统变量
log_output=[none|file|table|file,table] #通用查询日志输出格式
general_log=[on|off] #是否启用通用查询日志 general_log_file[=filename] #通用查询日志位置及名字
通用查询日志的备份
在linux或unix中，你可以通过下面的命令重新命名文件
并创建一个新文件：
shell> mv hostname.log hostname-old.log shell> mysqladmin flush-logs shell> cp hostname-old.log to-backup-directory shell> rm hostname-old.log
在windows中，服务器打开日志文件期间不能重新命名日志文件。必须先停止服务器然后重新命名日志文件。然后重启服务器来创建新日志文件。
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 | +------+------+
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。
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