如何查询MySql日志

今天美国老板发来一封email，一句What happen to ...? 其他任何线索没有，我的给出答案，一一排查，看能否找到问题缘由或是恢复数据，更新问题？程序问题？结果都是没有头绪，最后想了下mysql的日志看能否看看，以前没看过mysql的日志，查查资料，最终皇天不负有心人，搞定了，现在总结下：

1.首先确认你日志是否启用了

MySQL>show variables like 'log_bin'; 

2.如果启用了，即ON那日志文件就在MySQL的安装目录的data目录下

3.怎样知道当前的日志 

MySQL> show master status;  

4.看二进制日志文件用MySQLbinlog

shell>MySQLbinlog mail-bin.000001 

或者

shell>MySQLbinlog mail-bin.000001 | tail  
因为mail-bin.000001是二进制的日志，所以想看日志就需要用mysqlbinlog命令，将二进制文件转换为日志文件，下面详细说说如何使用：
上面已经说过如果启用了日志文件，那么默认的日志文件就在data目录下（如果你没有更改的话）
进入存放日志文件目录，使用
mysqlbinlog localhost-bin.000202 > new_file_name.log
命令，将目标文件保存为日志文件，可指定保存路径下
有个小技巧跟大家介绍下，我在准备转换的时候发现日志文件有2G多，寻思着为什么mysql为什么不把日志按日志定期的分多个文件放呢。结果发现mysql有个更好的方法，可以通过时间参数获取某个时间段的数据，例子如下：
mysqlbinlog    --start-datetime="2010-11-20 00:00:00"  --stop-datetime="2010-11-21 00:00:00" 
[hx@localhost data]$ mysqlbinlogmysqlbinlog Ver 3.0 for pc-linux-gnu at i686By Monty and Sasha, for your professional useThis software comes with NO WARRANTY: This is free software,and you are welcome to modify and redistribute it under the GPL license
Dumps a MySQL binary log in a format usable for viewing or for piping tothe mysql command line client
Usage: mysqlbinlog [options] log-files-d, --database=name List entries for just this database (local log only).-D, --disable-log-bin Disable binary log. This is useful, if you enabled--to-last-log and are sending the output to the sameMySQL server. This way you could avoid an endless loop.You would also like to use it when restoring after acrash to avoid duplication of the statements you alreadyhave. NOTE: you will need a SUPER privilege to use thisoption.-f, --force-read    Force reading unknown binlog events.-?, --help          Display this help and exit.-h, --host=name     Get the binlog from server.-o, --offset=#      Skip the first N entries.-p, --password[=name] Password to connect to remote server.-P, --port=#        Use port to connect to the remote server.-j, --position=#    Deprecated. Use --start-position instead.--protocol=name     The protocol of connection (tcp,socket,pipe,memory).-r, --result-file=name Direct output to a given file.-R, --read-from-remote-server Read binary logs from a MySQL server--open_files_limit=# Used to reserve file descriptors for usage by thisprogram-s, --short-form    Just show the queries, no extra info.-S, --socket=name   Socket file to use for connection.--start-datetime=name Start reading the binlog at first event having a datetimeequal or posterior to the argument; the argument must bea date and time in the local time zone, in any formataccepted by the MySQL server for DATETIME and TIMESTAMPtypes, for example: 2004-12-25 11:25:56 (you shouldprobably use quotes for your shell to set it properly).--stop-datetime=name Stop reading the binlog at first event having a datetimeequal or posterior to the argument; the argument must bea date and time in the local time zone, in any formataccepted by the MySQL server for DATETIME and TIMESTAMPtypes, for example: 2004-12-25 11:25:56 (you shouldprobably use quotes for your shell to set it properly).--start-position=# Start reading the binlog at position N. Applies to thefirst binlog passed on the command line.--stop-position=#   Stop reading the binlog at position N. Applies to thelast binlog passed on the command line.-t, --to-last-log   Requires -R. Will not stop at the end of the requestedbinlog but rather continue printing until the end of thelast binlog of the MySQL server. If you send the outputto the same MySQL server, that may lead to an endlessloop.-u, --user=name     Connect to the remote server as username.-l, --local-load=name Prepare local temporary files for LOAD DATA INFILE in thespecified directory.-V, --version       Print version and exit.
Variables (--variable-name=value)and boolean options {FALSE|TRUE} Value (after reading options)--------------------------------- -----------------------------database                          (No default value)disable-log-bin                   FALSEforce-read                        FALSEhost                              (No default value)offset                            0port                              3306position                          4read-from-remote-server           FALSEopen_files_limit                  64short-form                        FALSEsocket                            (No default value)start-datetime                    (No default value)stop-datetime                     (No default value)start-position                    4stop-position                     18446744073709551615to-last-log                       FALSEuser                              (No default value)local-load                        (No default value)
2009.09.30 检查一个应用的问题的时候，发现通过 oracle 的 dblink 连接 mysql 进行更新等操作的时候，mysql 不会把操作的 sql 语句记录到日志文件里，有点点郁闷了