曾经有朋友问我数据被删除了，不借助第三方工具能不能查是什么时候发生的。 SQL Server提供了一个undocumented的函数fn_dblog可以让我们查看活动的transaction log。
语法如下：
::fn_dblog(@StartingLSN,@EndingLSN)
如果参数都为NULL默认是抓取所有的交易信息。
使用这个函数我们可以查询DML,DDL信息，比如数据删除，修改更新等等。下面我们来看一个数据更新的例子：
create table test(namevarchar(10))
--插入条数据
insert into testvalues(\'allen test\')
go 5
---查询对表Test的修改
select [Transaction Name],Operation,AllocUnitId,AllocUnitName,[Begin Time]fromfn_dblog(null,null)
where AllocUnitName =\'dbo.test\'andOperation=\'LOP_INSERT_ROWS\'
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
NULLLOP_INSERT_ROWS72057594040090624 dbo.test NULL
NULLLOP_INSERT_ROWS72057594040090624 dbo.test NULL
NULLLOP_INSERT_ROWS72057594040090624 dbo.test NULL
NULLLOP_INSERT_ROWS72057594040090624 dbo.test NULL
NULLLOP_INSERT_ROWS72057594040090624 dbo.test
--删除表
drop table test
----从Log中查询对表的删除
select [Transaction Name],Operation,AllocUnitId,AllocUnitName,[Begin Time]fromfn_dblog(null,null)
where [Transaction Name] = \'DROPOBJ\'
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DROPOBJLOP_BEGIN_XACT NULL NULL
--查询Page Split
select Operation, AllocUnitName,COUNT(*)asNumberofIncidents
from ::fn_dblog(null,null)
where Operation =N\'LOP_DELETE_SPLIT\'
group byOperation, AllocUnitName
注意：从fn_dblog 查出来的LSN是不能直接作为参数的，需要将16进制转化为numeric：
The LSN we havefrom the log dump above is 0000009d:0000021e:0001.To convert it:
- Take the rightmost 4 characters (2-byte log record number) and convert to a 5-character decimal number, including leading zeroes, to get stringA
- Take the middle number (4-byte log block number) and convert to a 10-character decimal number, including leading zeroes, to get stringB
- Take the leftmost number (4-byte VLF sequence number) and convert to a decimal number, with no leading zeroes, to get stringC
- The LSN string we need is stringC + stringB + stringA
So0000009d:0000021e:0001 becomes \'157\' + \'0000000542\'+ \'00001\' =\'157000000054200001\'.（来自SQLSkills）
可以参考下面的脚本：
DECLARE @pageID$ NVARCHAR(23), @pageIDNVARCHAR(50), @sqlCmdNVARCHAR(4000);
SET @pageID$ =\'0001:0000004d\'--- PageID
SELECT @pageID =
CONVERT(VARCHAR(4),CONVERT(INT,CONVERT(VARBINARY,
SUBSTRING(@pageID$, 0, 5), 2)))
+ \',\' +
CONVERT(VARCHAR(8),CONVERT(INT,CONVERT(VARBINARY,
SUBSTRING(@pageID$, 6, 8), 2)))
---查看Page内容
SET @sqlCmd = \'DBCC PAGE (\'\'Crack_Me\'\',\'+ @pageID + \',3) WITH TABLERESULTS\'
EXECUTE(@sqlCmd)
另外这个函数只能对当前活动的Log生效，如果Log备份之后就无法读取了，我们需要用另外一个函数（fn_dump_dblog http://blog.csdn.net/smithliu328/article/details/7817540）从备份中读取。上面也只是能够看到数据被修改，但是无法做到恢复数据。
目前网上有人做了一些脚本可以实现恢复，我现在正在做测试，如果能够成功的话后面会把脚本发出来。
转载于：http://blog.csdn.net/kevinsqlserver/article/details/7800628
-- select * FROM fn_dblog(null,null)