恢复SQLSERVER被误删除的数据

发布时间：2020-12-12 12:55:26 所属栏目：MsSql教程来源：网络整理

导读：恢复SQLSERVER被误删除的数据曾经想实现Log Explorer for SQL Server的功能，利用ldf里面的日志来还原误删除的数据这里有一篇文章做到了，不过似乎不是所有的数据类型都支持以下为译文： http://raresql.com/2011/10/22/how-to-recover-deleted-data-from

恢复SQLSERVER被误删除的数据

曾经想实现Log Explorer for SQL Server的功能，利用ldf里面的日志来还原误删除的数据

这里有一篇文章做到了，不过似乎不是所有的数据类型都支持

以下为译文：http://raresql.com/2011/10/22/how-to-recover-deleted-data-from-sql-sever/

在我使用SQLSERVER的这些年里面，大部分人都会问我一个问题：“能不能恢复被删除的数据？？”

现在，从SQLSERVER2005 或以上版本能很容易能够恢复被删除的数据

（注意：这个脚本能恢复下面的数据类型的数据而且兼容CS 排序规则）

image
text
uniqueidentifier
tinyint
smallint
int
smalldatetime
real
money
datetime
float
sql_variant
ntext
bit
decimal
numeric
smallmoney
bigint
varbinary
varchar
binary
char
timestamp
nvarchar
nchar
xml
sysname

让我来用demo来解释一下我是怎么做到的

USE master
GO
--创建数据库
CREATE DATABASE test
GO

USE [test]
GO


创建表
TABLE dbo].aa](
    id] intIDENTITY(1,1) NOT NULL,NAMEnvarchar](200) NULL
) ON PRIMARY插入测试数据
INSERT ]
        ( ] )
SELECT '你好'
GO



删除数据
Delete from aa
Go



验证数据是否已经删除
Select * Go

现在你需要创建一个存储过程来恢复你的数据

 Script Name: Recover_Deleted_Data_Proc
-- Script Type : Recovery Procedure  Develop By: Muhammad Imran Date Created: 15 Oct 2011 Modify Date: 22 Aug 2012 Version    : 3.1 Notes : Included BLOB data types for recovery.& Compatibile with Default,CS collation,Arabic_CI_AS.
 

PROCEDURE Recover_Deleted_Data_Proc
    @Database_Name NVARCHAR(MAX),@SchemaName_n_TableName @Date_From DATETIME = 1900/01/01',0);">@Date_To 9999/12/31AS
    DECLARE @RowLogContents VARBINARY(8000)
    @TransactionID MAX)
    @AllocUnitID BIGINT
    @AllocUnitName @SQL @Compatibility_Level INT
 
 
    SELECT  @Compatibility_Level = dtb.compatibility_level
    FROM    master.sys.databases AS dtb
    WHERE   dtb.name = @Database_Name
 
    IF ISNULL(@Compatibility_Level,0); ">0) <= 80
        BEGIN
            RAISERROR(The compatibility level should be equal to or greater SQL SERVER 2005 (90)',0); ">16,0); ">1)
            RETURN
        END
 
    IF ( COUNT(*)
         FROM   INFORMATION_SCHEMA.TABLES
         WHERE  TABLE_SCHEMA] + .' TABLE_NAME@SchemaName_n_TableName
       ) = 0
        Could not found the table in the defined database@bitTable TABLE
        (
          ID] INT,0);">BitvalueINT
        )
Create table to set the bit position of one byte.
 
    INSERT  INTO @bitTable
            SELECT  0,2
            UNION ALL
            1,0); ">2,0); ">4
            3,0); ">8
            4,0); ">16
            5,0); ">32
            6,0); ">64
            7,0); ">128
 
Create table to collect the row data.
    @DeletedRecords Row IDINT 1),0);">RowLogContents8000),0);">AllocUnitIDBIGINT,0);">Transaction IDFixedLengthDataSMALLINT,0);">TotalNoOfColsNullBitMapLengthNullBytesTotalNoofVarColsColumnOffsetArrayVarColumnStartSlot IDNullBitMapVARCHAR(MAX)
        )
Create a common table expression to get all the row data plus how many bytes we have for each row.
;
    WITH    RowData
              AS ( SELECT   RowLog Contents 0AS ],0);">]  
 
[Fixed Length Data] = Substring (RowLog content 0,Status Bit A+ Status Bit B + 1,2 bytes)
,255);">CONVERT(SMALLINT,BINARY(2),255);">REVERSE(SUBSTRING(2 + 2)))) ]  @FixedLengthData
 
 [TotalnoOfCols] =  Substring (RowLog content 0,[Fixed Length Data] + 1,255);">INT,0); ">2)))) ]
 
[NullBitMapLength]=ceiling([Total No of Columns] /8.0)
,255);">CEILING(/ 8.0)) ] 
 
[Null Bytes] = Substring (RowLog content 0,Status Bit A+ Status Bit B + [Fixed Length Data] +1,[NullBitMapLength] )
,0); ">8.0))) [TotalNoofVarCols] = Substring (RowLog content 0,[Null Bitmap length] + 2 )
,( CASE WHEN ],128);">IN (
                                        0x10,0); ">0x30,0); ">0x70 )
                                   THEN 3
                                                              8.0)),0); ">2))))
                                   ELSE NULL
                              END ) [ColumnOffsetArray]= Substring (RowLog content 0,[Null Bitmap length] + 2,[TotalNoofVarCols]*2 )
,0); ">3
                                                  8.0))
                                                  IN ( 0x10,0); ">0x70 )
                                                         2))))
                                                         NULL
                                                    END ) * 2)
                                     Variable column Start = Status Bit A+ Status Bit B + [Fixed Length Data] + [Null Bitmap length] + 2+([TotalNoofVarCols]*2)
,128);">IN (
                                      0x70 )
                                 THEN ( 4
                                        8.0))
                                        + ( ( 0x70 )
                                                   2))))
                                                   NULL
                                              2 ) )
                                 NULL
                            END ]
                   FROM     sys.fn_dblog(NULL,NULL)
                   WHERE    AllocUnitId IN (
                            SELECT  Allocation_unit_id]
                            FROM    sys.allocation_units allocunits
                                    INNER JOIN sys.partitions partitions ON ( allocunits.type IN (
                                                              3 )
                                                              AND partitions.hobt_id = allocunits.container_id
                                                              )
                                                              OR ( allocunits.type 2
                                                              AND partitions.partition_id = allocunits.container_id
                                                              )
                            WHERE   object_id OBJECT_ID(''
                                                          + @SchemaName_n_TableName
                                                          '') )
                            AND Context IN ( LCX_MARK_AS_GHOSTLCX_HEAP' )
                            AND Operation LOP_DELETE_ROWSAND 0x70 )
 
/*Use this subquery to filter the date*/
                            TRANSACTION IDSELECT DISTINCT
                                    FROM    sys.fn_dblog(NULL)
                            WHERE   Context LCX_NULL' )
                                    LOP_BEGIN_XACTTransaction NameDELETEuser_transactionNVARCHAR(11),0);">Begin Time]) BETWEEN @Date_From
                                                              AND
                                                              @Date_To )
                 ),128);">Use this technique to repeate the row till the no of bytes of the row.
            N1 ( n )
              SELECT   1
                   ALL
                   1
                 ),N2 ( n )
              FROM     N1 AS X,N1 AS Y
                 ),N3 ( n )
              FROM     N2 SELECT   ROW_NUMBER() OVER ( ORDER BY X.n )
                   FROM     N3 AS Y
                 )
        @DeletedRecords
                SELECT  RowLogContents,0);">]
         -Get the Null value against each column (1 means null zero means not null)
,128);">= ( REPLACE(STUFF(( SELECT
                                                              ,0);">'
                                                              + ( CASE
                                                              0
                                                              1),( SUBSTRING(NullBytes,n,128);">% 2 ))
                                                              ELSE 1)
                                                              / ] )
                                                              as [nullBitMap]
                                                         FROM N4 AS Nums
                                                              JOIN RowData AS C ON n <= NullBitMapLength
                                                              CROSS JOIN @bitTable
                                                         WHERE
                                                              C.= D.]
                                                         BY ASC
                                                       FOR
                                                         XML PATH('')
                                                       ),0);">''),0);">'') )
                FROM    RowData D
 
    FROM   @DeletedRecords
       ) There is no data in the log as per the search criteria@ColumnNameAndData RowlogcontentsVARBINARY(] SYSNAME,0);">nullbitleaf_offsetlengthsystem_type_idTINYINT,0);">bitposxprecxscaleis_nullColumn value SizeColumn Lengthhex_ValueUpdateINT
        )
 
Create common table expression and join it with the rowdata table to get each column details
/*This part is for variable data columns*/
@RowLogContents,128);">(col.columnOffValue - col.columnLength) + 1,128);">col.columnLength)
    @ColumnNameAndData
            AS nullbit,leaf_offset,255);">ISNULL(syscolumns.length,cols.max_length) AS bitpos,255);">ISNULL(syscolumns.xprec,cols.precision) AS xprec,255);">ISNULL(syscolumns.xscale,cols.scale) AS xscale,0);">nullBitMap1) AS is_null,255);">WHEN leaf_offset < 1
                                0
                           * leaf_offset
                                                              -1 ) - > 30000
                                       2))))
                                            - POWER(2,0); ">15)
                                       2))))
                                  END )
                      30000
                                            ISNULL(NULLIF(* ( ( leaf_offset
                                                              1 ) )
                                                              2)))),0); ">0),0);">varColumnStartSystem_type_idIN (
                                                        35,0); ">34,0); ">99 ) THEN 16
                                                   ELSE 24
                                              END )
                                       24 
                                       2))))
                                              ]) )
                                       15)
                                            ])
                                  1
                           THEN NULL
                           SUBSTRING(Rowlogcontents,( ( 30000
                                                   2))))
                                                        15)
                                                   2))))
                                              END )
                                            - ( 30000
                                                          30000
                                                     99 )
                                                              16
                                                              24
                                                            24 
                                                     2))))
                                                          ])
                                                     15)
                                                          ])
                                                END ) ) 30000
                                                      30000
                                                 99 )
                                                             16
                                                             24
                                                        24 
                                                 ABS(]))
                                                 15)
                                                      2))))
                                                      ])
                                            END ))
                      AS hex_Value,0); ">0
            FROM    @DeletedRecords A
                    JOIN sys.allocation_units allocunits ON A.AllocUnitId= allocunits.Allocation_Unit_Id]
                    = allocunits.container_id
                                                            )
                                                            = allocunits.container_id
                                                              )
                    JOIN sys.system_internals_partition_columns cols ON cols.partition_id = partitions.partition_id
                    LEFT OUTER JOIN syscolumns ON syscolumns.id = partitions.object_id
                                                  AND syscolumns.colid = cols.partition_column_id
            WHERE   leaf_offset UNION
This part is for fixed data columns*/
            TOP 1
                                SUM(WHEN C.leaf_offset 1
                                                THEN max_length
                                                0
                                           END),0); ">0)
                      FROM      sys.system_internals_partition_columns C
                      WHERE     cols.partition_id = C.partition_id
                                AND C.leaf_null_bit < cols.leaf_null_bit
                    ) 5 1
                         NULL
                         1
                                                    1
                                                              AND C.leaf_bit_position THEN max_length
                                                              0)
                                          FROM      sys.system_internals_partition_columns C
                                          = C.partition_id
                                                    < cols.leaf_null_bit
                                        ) BY nullbit
 
    @BitColumnByte AS INT
    @BitColumnByte *) 8.0))
    @ColumnNameAndData
    System_Type_id104;
    WITH    N1 ( n )
              SELECT   RowLogContents,0);">BitMapSUBSTRING(( SUBSTRING(hex_Value,128);">as [nullBitMap]
                                                              FROM
                                                              N4 @ColumnNameAndData
                                                              <= @BitColumnByte
                                                              104
                                                              AND bitpos @bitTable
                                                              ]
                                                              ASC
                                                              FOR
                                                              XML
                                                              PATH('')
                                                              ),0);">''),0);">'') ),bitpos 1)))
                   FROM     @ColumnNameAndData D
                   WHERE    104
                 )
        UPDATE  A
        SET     ]
        @ColumnNameAndData A
                JOIN CTE B = B.]
                                    AND A.]
 
 
*************Check for BLOB DATA TYPES******************************/
    @Fileid @Pageid @Slotid @CurrentLSN @LinkID @Context VARCHAR(50)
    @ConsolidatedPageID @LCX_TEXT_MIX MAX)
 
    @temppagedata ParentObjectObjectFieldValue] SYSNAME
        )
 
    @pagedata Page IDFile IDSPage IDS@ModifiedRawData PAGE IDFILE IDSPAGE IDSRowLog Contents 0_varRowLog Length50),0);">RowLog LenLink IDINT DEFAULT ( 0 ),255);">INT
        )
 
    DECLARE Page_Data_Cursor CURSOR
    FOR
        We need to filter LOP_MODIFY_ROW,LOP_MODIFY_COLUMNS from log for deleted records of BLOB data type& Get its Slot No,Page ID & AllocUnit IDLTRIM(RTRIM(DescriptionDeallocated''))) NULL NULL)
            WHERE   AllocUnitId IN (
                    FROM    sys.allocation_units allocunits
                            '' @SchemaName_n_TableName
                                                  '') )
                    LOP_MODIFY_ROW' )
                    ContextLCX_PFSAND Description LIKE %Deallocated%'
            */
                    DISTINCT
                            NULL)
                    '
                            @Date_To )
            GROUP UNION
            15,255);">LEN(])) 7,0); ">2)),Context ,CAST(RIGHT([Current LSN],4) AS INT) AS [Current LSN]
            LCX_TEXT_MIX' ) 
            @Date_To )
                         
            ***************************************/
 
    OPEN Page_Data_Cursor
 
    FETCH NEXT FROM Page_Data_Cursor @ConsolidatedPageID,0);">@Slotid,0);">@AllocUnitID,0);">@LCX_TEXT_MIX,0);">@LinkID,0);">@Context
 
    WHILE @@FETCH_STATUS @hex_pageid MAX)
            Page ID contains File Number and page number It looks like 0001:00000130.
              In this example 0001 is file Number &  00000130 is Page Number & These numbers are in Hex formatSET @Fileid SUBSTRING(CHARINDEX(:@ConsolidatedPageID))  Seperate File ID from Page ID
         
            @hex_pageid 0x@ConsolidatedPageID,0);">@ConsolidatedPageID)
                                               LEN(@ConsolidatedPageID))  -Seperate the page ID
            @Pageid CAST('' AS XML).value(xs:hexBinary(substring(sql:variable("@hex_pageid"),sql:column("t.pos")) )varbinary(max)'))  Convert Page ID from hex to integer
            FROM    ( SELECT    CASE @hex_pageid,0); ">2)
                                  ' 3
                                  0
                                END
                    ) AS t ( pos ) 
             
            IF @Context '
                BEGIN
                    DELETE  @temppagedata
                    @temppagedata
                            EXEC
                                ( DBCC PAGE(@DataBase_Name '
                                  @fileid @pageid
                                  '
                                ); 
                    @pagedata
                            @fileid,0);">@pageid,0);">@AllocUnitID,0);">@temppagedata
                END
            ELSE
                '
                    BEGIN
                        @ModifiedRawData
                                VARBINARY,0);">@LCX_TEXT_MIX,0); ">11,0); ">2)))),0);">@LinkID,0); ">0
                    END    
            @Context
        END
     
    CLOSE Page_Data_Cursor
    DEALLOCATE Page_Data_Cursor
 
    @Newhexstring MAX);
 
    The data is in multiple rows in the page,so we need to convert it into one row as a single hex value.
    This hex value is in string format
    @ModifiedRawData
            ( ]
            )
            SlotOffset])
                                4 ) )
                              2) SUBSTRING(( ?])
                                                              ])),0);">'')
                                                        FROM  @pagedata C
                                                        WHERE B.= C.]
                                                              SUBSTRING(B.4 ) )) SUBSTRING(C.4 ) ))
                                                              %Memory Dump%'
                                                        LEFT(1)
                                                      FOR
                                                        XML PATH('')
                                                      ),0);">' '')
                              ),0); ">20000) '
                                        '')
                                                          FROM
                                                              @pagedata C
                                                          WHERE
                                                              B.'
                                                          1)
                                                        FOR
                                                          XML PATH('')
                                                        ),0); ">4) Length]
            @pagedata B
            ]]
 
    UPDATE  @ModifiedRawData
    8000),0);">xs:hexBinary(substring(sql:column("[RowLog Length]"),0))varbinary(Max)')))
    LINK ID0
 
    xs:hexBinary(substring(sql:column("[RowLog Contents 0_var]"),0);">')
    UPDATE  B
    SET     B.WHEN A.IS NULL
                                                AND C.NULL
                                           THEN A.]
                                                + C.]
                                           IS THEN C.]
                                      END ),255);">ISNULL(B.1
    @ModifiedRawData B
            @ModifiedRawData A MAX),0); ">15 14,0); ">19 ]
            @ModifiedRawData C ON C.27 31 ]
    WHERE   ( A.NULL
              OR C.NULL
            )
 
 
    END )
    <> B.]
                                            AND B.0
            0
    NULL
            )
 
    >= 8000
                                         15,0);">])
                                         6)))))
                                    ] 
    @ColumnNameAndData A
            @ModifiedRawData B hex_value17,0); ">4)))) ]
                                             9,0); ">2)) System_Type_Id99,0); ">167,0); ">175,0); ">231,0); ">239,0); ">241,0); ">165,0); ">98 )
            <> 0 
 
    WHEN B.NULL
                                      NULL
                                 THEN B.]
                                      ]
                                 @ColumnNameAndData A
            5,128);">AND ( B.NULL
                  NULL
                )
 
    3,0); ">99 )
            0 
     
    0xFFFE ]))
    241
 
    #temp_Data]
        (
          FieldNameFieldValueINTO #temp_Data
            SELECT  NAME,255);">WHEN system_type_id 239 )
                         NVARCHAR,NCHAR
                         175 )
                         VARCHAR,CHAR
                         35 )
                         Text
                         99 )
                         nText 
                         48
                         TINYINT,255);">REVERSE(hex_Value)))) TINY INTEGER
                         52
                         SMALL INTEGER
                         56
                         4),128);"> INTEGER
                         127
                         BIGINT,0); ">8),255);">REVERSE(hex_Value)))) BIG INTEGER
                         61
                         DATETIME,255);">REVERSE(hex_Value))),0); ">100) DATETIME
                         58
                         SMALLDATETIME,128);">SMALL DATETIME
                         108
                         CONVERT(NUMERIC(38,0); ">20),xprec)
                              + hex_Value)) - NUMERIC
                         106
                         DECIMAL(- DECIMAL
                         60,0); ">122 )
                         MONEY,128);">MONEY,SMALLMONEY
                         104
                         CONVERT (BIT,hex_Value)
                              2))   BIT
                         62
                         STR(FLOAT,255);">SIGN(REVERSE(hex_Value)) BIGINT))
                                              * ( 1.0
                                                  BIGINT)
                                                      & 0x000FFFFFFFFFFFFF )
                                                  * POWER(CAST(2 FLOAT),0); ">52) )
                                              BIGINT)
                                                          0x7ff0000000000000 )
                                                        EXP(52 LOG(2))
                                                        1023 ))),0); ">53,255);">LEN(hex_Value)))) - FLOAT
                         59
                         BIGINT))
                                             1.0
                                                 BIGINT)
                                                     0x007FFFFF )
                                                 REAL),0); ">23) )
                                             REAL),( ( ( INT) )
                                                         0x7f800000 )
                                                       23 2))
                                                       127 )) 23,0); ">23)),0); ">8) Real
                         173 )
                         CHARINDEX(0x,0);">xs:hexBinary(sql:column("hex_Value"))VARBINARY(8000)')) 0
                                     '
                                     ''
                                varchar(max)')  BINARY,VARBINARY
                         34
                         ')  IMAGE
                         36
                         UNIQUEIDENTIFIER,hex_Value)) UNIQUEIDENTIFIER
                         231
                         CONVERT(SYSNAME,128);">SYSNAME
                         241
                         CONVERT(XML,128);">XML
                         189
                         TIMESTAMP
                         98
                         SUBSTRING(hex_Value,0); ">1)) 56
                                     LEN(hex_Value))))))   INTEGER
                                     108
                                     38,0); ">1))
                                          4,0); ">0)
                                          - NUMERIC
                                     167
                                     9,255);">LEN(hex_Value))))) 36
                                     SUBSTRING(( hex_Value ),0); ">20))) UNIQUEIDENTIFIER
                                     61
                                     LEN(hex_Value))))),128);">DATETIME
                                     165
                                     '
                                          0
                                                             '
                                                             ''
                                                        END )
                                                      '),255);">LEN(hex_Value)) END )
                    AS FieldValue,255);">BY nullbit
 
Create the column name in the same order to do pivot table.
 
    @FieldName @FieldName '
                                    QUOTENAME(Name]) MAX))
                             FROM   syscolumns
                             WHERE  id ''
                                                   @SchemaName_n_TableName
                                                   '')
                           FOR
                             XML PATH('')
                           ),0);">'')
 
Finally did pivot table and get the data back in the same format.
 
    @sql SELECT @FieldName
         FROM #temp_Data PIVOT (Min([FieldValue]) FOR FieldName IN ('
        )) AS pvt'
    EXEC sp_executesql @sql
 
GO

恢复你的数据

恢复数据，不加时间段条件参数：数据库名，表名EXAMPLE #1 : FOR ALL DELETED RECORDS EXEC Recover_Deleted_Data_Proc 'dbo.恢复数据，加时间段条件EXAMPLE #2 : FOR ANY SPECIFIC DATE RANGE 2014-04-23'

执行了下面的存储过程之后你会发现会显示出刚才删除的数据

dbo.aaGO

解释

究竟他是如何工作的?让我们来一步一步来,这个过程涉及到7个步骤:

步骤1:

我们需要获得SQLSERVER删除的数据记录.使用标准SQLSERVER函数fn_dblog，我们能够容易的获得事务日志记录（包括

已删的数据。不过，我们只需要事务日志中选中的被删数据，所以我们的过滤条件需要包含3个字段 Context,Operation &?AllocUnitName）

We need to get the deleted records from?sql?server. By using the standard SQL Server function?fn_blog,we can easily get all transaction log (Including deleted data. But,we need only the selected deleted records from the transaction log. So we included three filters (Context,Operation,AllocUnitName).

Context (‘LCX_MARK_AS_GHOST’and?‘LCX_HEAP’)
Operation (‘LOP_DELETE_ROWS’)
AllocUnitName(‘dbo.aa’) –- Schema + table Name

Context可以说明是堆表还是聚集表

Operation：删除操作

AllocUnitName：分配单元名称，表名

下面是一个代码片段

NULL) WHERE AllocUnitName ' ) ' )

这个查询会返回不同列的信息，但是我们只需要选择[RowLog Contents 0]列，去获得被删除的数据的内容

RowLog?content 0列的内容类似于这样

“0x300018000100000000000000006B0000564920205900000

00500E001002800426F62206A65727279″

步骤2:

现在，我们已经删除了数据，这些数据以hex码的形式放在事务日志里，这些hex码是有规律的，我们根据这些规律可以很容易恢复这些数据。

不过在恢复这些数据之前，我们需要理解这些格式。这些格式在KalenDelaney’s SQL Internal’s book.的书里面有讲解

1 Byte : Status Bit A
1 Byte : Status Bit B
2 Bytes : Fixed length size
n Bytes : Fixed length data
2 Bytes : Total Number of Columns
n Bytes : NULL Bitmap (1 bit for each column as 1 indicates that the column is null and 0 indicate that the column is not null)
2 Bytes : Number of variable-length columns
n Bytes : Column offset array (2x variable length column)
n Bytes : Data for variable length columns

所以,hex码的“RowLog?content 0″列的内容就等价于

“Status Bit A +Status Bit B +Fixed length size +Fixed length data +Total Number of Columns +NULL Bitmap +Number of variable-length columns +NULL Bitmap+Number of variable-length columns +Column offset array +Data for variable length columns.”

更详细的可以参考：SQL Server2008存储结构之堆表、行溢出

关于数据行的结构我们还可以采用稍微宏观一些的视角来查看。

?

　　

步骤3:

现在，我们需要解剖RowLog Content o列的内容（我们删除的数据的Hex码），利用上面的数据行的结构

[Fixed Length Data]?= Substring (RowLog?content 0,?Status Bit A+Status Bit B?+ 1,2 bytes)
[Total No of Columns]= Substring (RowLog?content 0,?[Fixed Length Data]?+ 1,2 bytes)
[Null Bitmap length]?= Ceiling?([Total No of Columns]/8.0)
[Null Bytes]= Substring (RowLog?content 0,0);">Status Bit A+?Status Bit B?+[Fixed Length Data]?+1,?[Null Bitmap length]?)
Total no of variable columns?= Substring (RowLog?content 0,0);">?Status Bit A+?Status Bit B?+?[Fixed Length Data]?+1,?[Null Bitmap length]?+ 2 )
Column Offset Array= Substring (RowLog?content 0,?[Null Bitmap length]?+ 2,?Total no of variable columns*2 )
Variable Column Start =??Status Bit B?+?[Fixed Length Data]?+?[Null Bitmap length]?+ 2+(?Total no of variable columns*2)

步骤4:

现在我们已经将hex码切开了(0x300008000100000002000001001300604F7D59),所以,我们能找到删除的行的某列的数据是否为null值

根据NULL位图。为了完成将NULL Bytes的hex码转换为二进制格式（正如之前讨论的，1表示行中对应的那一列为null，而0则表示对应的列有实际的数据）

如果还不是明白的童鞋可以看一下我写的这篇文章：《SQLSERVER中NULL位图的作用》

步骤5:

现在，我们已经做了初步的数据分割?(Step-3) 和null值判断(Step-4) 。然后我们需要使用代码片段去获得列数据，例如：列名，列大小，精度，范围

和最重要的叶子的null位（确保列数据是固定长度的（<=-1表示固定长度）或者可变长度的（>=1））

使用下面的SQL语句

* FROM sys.allocation_units allocunits 3 ) = allocunits.container_id ) 2 = allocunits.container_id ) = partitions.partition_id object_id = cols.partition_column_id

与(Step-1,2,3,4) 获得的数据表做join连接，根据allocunits.[Allocation_Unit_Id]。

现在我们知道表和表中的数据信息，那么我们需要利用这些数据去将?[RowLog?Contents 0] 列里的hex码的数据插入到表中的相应列

现在我们需要关心每一列的数据究竟是固定长度的还是可变长度的

步骤6:

我们收集了每列的hex格式的数据。现在我们需要利用[System_type_id]去转换这些数据回去正确的数据类型

每一种数据类型都有不同的数据类型转换机制。

IN (239) THEN max),hex_Value))) 175) max),255);">REPLACE(hex_Value,0); ">0x00,0); ">0x20)))) TINY INTEGER 48 REVERSE (hex_Value)))) SMALL INTEGER 52 INTEGER 56 REVERSE(hex_Value)))) BIG INTEGER 127 DATETIME 61 Then Max),255);">Convert(REVERSE (hex_Value))),0); ">100) SMALL DATETIME =58 SMALL DATETIME - NUMERIC 108 18,0); ">14),xprec)++ hex_Value) as FLOAT)) In(122) Reverse(hex_Value))),0); ">2) - DECIMAL 106 Decimal(34),128);"> BIT 104 %2)) - FLOAT 62 Str(Reverse(hex_Value)) BIGINT)) * (1.0 + (BIGINT) 0x000FFFFFFFFFFFFF) FLOAT),0); ">52)) 0x7ff0000000000000) 2))1023))),0); ">53,255);">LEN(hex_Value)))) REAL When system_type_id 59 THEN Left(Cast(BIGINT))0x007FFFFF) Real),0); ">23)) INT) )0x7f800000)127))23,0); ">8) BINARY,VARBINARY In (173) THEN (Charindex(0x,255);">cast(xs:hexBinary(sql:column("hex_value"))0 END) ') UNIQUEIDENTIFIER 36

步骤7:

最终我们做一个数据透视表，你会看到最后的结果：被删的数据回来了！

注意：这些数据只是展示出来并没有自动插入回表中，你需要将这些数据重新插入回去表中！

我的测试

经过测试，作者写的这个存储过程还是有些问题

如果你创建的测试表的数据类型有xml或者是一些text数据类型的字段会有报错

Msg 537,255);">Level Procedure Recover_Deleted_Data_Proc,Line 525
Invalid length parameter passed to the or SUBSTRING function.

Msg 9420,0); ">651
XML parsing: line character character

但是一般的数据类型则不会，例如nvarchar这些

还有不要在存储过程的最后加

Recover the deleted data without date range dbo.Test_TableRecover the deleted data it with date range 2012-06-012012-06-30否则会报错

消息 50000，级别 16，状态 1，过程 Recover_Deleted_Data_Proc，第 290 行
There is no data in the log as per the search criteria

总结

实际上这个存储过程还是挺有研究意义的，对于想做一个跟Log Explorer for SQL Server软件功能差不多的软件出来

还是有可能的，跟着作者的思路，一步一步实现

苦于最近太忙，先分享出来，以后再研究这个存储过程了~

如有不对的地方，欢迎大家拍砖o(∩_∩)o?

转自：http://www.cnblogs.com/lyhabc/p/3683147.html

（编辑：李大同）

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