I was working on “How to recover truncated data from SQL Server” from last couple of weeks and finally I was successful.
Now, it is very easy to recover truncated data from your SQL server 2005 or above.(Note: This script can recover following data types & compatible with CS collation.Also, your database recovery model should be FULL).
- tinyint
- smallint
- int
- bigint
- bit
- char
- varchar
- nchar
- nvarchar
- datetime
- smalldatetime
- money
- smallmoney
- decimal
- numeric
- real
- float
- binary
- varbinary
- uniqueidentifier
Let me explain this issue demonstrating simple example.
--Create Table
CREATE TABLE [dbo].[Student](
[Sno] [int] NOT NULL,
[Student ID] nvarchar(6) Not NULL ,
[Student name] [varchar](50) NOT NULL,
[Date of Birth] datetime not null,
[Weight] [int] NULL)
--Insert data into table Insert into dbo.[Student] values (1,'STD001','Bob','2003-12-31',40) Insert into dbo.[Student] values (2,'STD002','Alexander','2004-11-15',35) --Check the existence of the data Select * from dbo.[Student]
--truncate data Truncate Table dbo.Student --Verify the data has been truncated Select * from dbo.[Student]
Now, you need to create this procedure to recover your truncated data
Create PROCEDURE Recover_Truncated_Data_Proc
@Database_Name NVARCHAR(MAX),
@SchemaName_n_TableName NVARCHAR(MAX),
@Date_From datetime='1900/01/01',
@Date_To datetime ='9999/12/31'
AS
DECLARE @Fileid INT
DECLARE @Pageid INT
DECLARE @Slotid INT
DECLARE @ConsolidatedPageID VARCHAR(MAX)
Declare @AllocUnitID as bigint
Declare @TransactionID as VARCHAR(MAX)
/* Pick The actual data
*/
declare @temppagedata table
(
[ParentObject] sysname,
[Object] sysname,
[Field] sysname,
[Value] sysname)
declare @pagedata table
(
[Page ID] sysname,
[AllocUnitId] bigint,
[ParentObject] sysname,
[Object] sysname,
[Field] sysname,
[Value] sysname)
DECLARE Page_Data_Cursor CURSOR FOR
/*We need to filter LOP_MODIFY_ROW,LOP_MODIFY_COLUMNS from log for modified records & Get its Slot No, Page ID & AllocUnit ID*/
SELECT LTRIM(RTRIM(Replace([Description],'Deallocated',''))) AS [PAGE ID]
,[Slot ID],[AllocUnitId]
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 (1, 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 Operation IN ('LOP_MODIFY_ROW') AND [Context] IN ('LCX_PFS')
AND Description Like '%Deallocated%'
/*Use this subquery to filter the date*/
AND [TRANSACTION ID] IN (SELECT DISTINCT [TRANSACTION ID] FROM sys.fn_dblog(NULL, NULL)
WHERE Context IN ('LCX_NULL') AND Operation in ('LOP_BEGIN_XACT')
AND [Transaction Name]='TRUNCATE TABLE'
AND CONVERT(NVARCHAR(11),[Begin Time]) BETWEEN @Date_From AND @Date_To)
/****************************************/
GROUP BY [Description],[Slot ID],[AllocUnitId]
ORDER BY [Slot ID]
OPEN Page_Data_Cursor
FETCH NEXT FROM Page_Data_Cursor INTO @ConsolidatedPageID, @Slotid,@AllocUnitID
WHILE @@FETCH_STATUS = 0
BEGIN
DECLARE @hex_pageid AS VARCHAR(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 format*/
SET @Fileid=SUBSTRING(@ConsolidatedPageID,0,CHARINDEX(':',@ConsolidatedPageID)) -- Seperate File ID from Page ID
SET @hex_pageid ='0x'+ SUBSTRING(@ConsolidatedPageID,CHARINDEX(':',@ConsolidatedPageID)+1,Len(@ConsolidatedPageID)) ---Seperate the page ID
SELECT @Pageid=Convert(INT,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 substring(@hex_pageid, 1, 2) WHEN '0x' THEN 3 ELSE 0 END) AS t(pos)
DELETE @temppagedata
-- Now we need to get the actual data (After truncate) from the page
INSERT INTO @temppagedata EXEC( 'DBCC PAGE(' + @DataBase_Name + ', ' + @fileid + ', ' + @pageid + ', 1) with tableresults,no_infomsgs;');
---Check if any index page is there
If (Select Count(*) From @temppagedata Where [Field]='Record Type' And [Value]='INDEX_RECORD')=0
Begin
DELETE @temppagedata
INSERT INTO @temppagedata EXEC( 'DBCC PAGE(' + @DataBase_Name + ', ' + @fileid + ', ' + @pageid + ', 3) with tableresults,no_infomsgs;');
End
Else
Begin
DELETE @temppagedata
End
INSERT INTO @pagedata SELECT @ConsolidatedPageID,@AllocUnitID,[ParentObject],[Object],[Field] ,[Value] FROM @temppagedata
FETCH NEXT FROM Page_Data_Cursor INTO @ConsolidatedPageID, @Slotid,@AllocUnitID
END
CLOSE Page_Data_Cursor
DEALLOCATE Page_Data_Cursor
DECLARE @Newhexstring VARCHAR(MAX);
DECLARE @ModifiedRawData TABLE
(
[ID] INT IDENTITY(1,1),
[PAGE ID] VARCHAR(MAX),
[Slot ID] INT,
[AllocUnitId] BIGINT,
[RowLog Contents 0_var] VARCHAR(MAX),
[RowLog Contents 0] VARBINARY(8000)
)
--The truncated 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
INSERT INTO @ModifiedRawData ([PAGE ID],[Slot ID],[AllocUnitId]
,[RowLog Contents 0_var])
SELECT [Page ID],Substring([ParentObject],CHARINDEX('Slot', [ParentObject])+4, (CHARINDEX('Offset', [ParentObject])-(CHARINDEX('Slot', [ParentObject])+4)) ) as [Slot ID]
,[AllocUnitId]
,(
SELECT REPLACE(STUFF((SELECT REPLACE(SUBSTRING([Value],CHARINDEX(':',[Value])+1,CHARINDEX('†',[Value])-CHARINDEX(':',[Value])),'†','')
FROM @pagedata C WHERE B.[Page ID]= C.[Page ID] And Substring(B.[ParentObject],CHARINDEX('Slot', B.[ParentObject])+4, (CHARINDEX('Offset', B.[ParentObject])-(CHARINDEX('Slot', B.[ParentObject])+4)) )=Substring(C.[ParentObject],CHARINDEX('Slot', C.[ParentObject])+4, (CHARINDEX('Offset', C.[ParentObject])-(CHARINDEX('Slot', C.[ParentObject])+4)) ) And
[Object] Like '%Memory Dump%'
FOR XML PATH('') ),1,1,'') ,' ','')
) AS [Value]
From @pagedata B
Where [Object] Like '%Memory Dump%'
Group By [Page ID],[ParentObject],[AllocUnitId]
Order By [Slot ID]
-- Convert the hex value data in string, convert it into Hex value as well.
UPDATE @ModifiedRawData SET [RowLog Contents 0] = cast('' AS XML).value('xs:hexBinary(substring(sql:column("[RowLog Contents 0_var]"), 0) )', 'varbinary(max)')
FROM @ModifiedRawData
DECLARE @RowLogContents VARBINARY(8000)
Declare @AllocUnitName NVARCHAR(Max)
Declare @SQL NVARCHAR(Max)
DECLARE @bitTable TABLE
(
[ID] INT,
[Bitvalue] INT
)
----Create table to set the bit position of one byte.
INSERT INTO @bitTable
SELECT 0,2 UNION ALL
SELECT 1,2 UNION ALL
SELECT 2,4 UNION ALL
SELECT 3,8 UNION ALL
SELECT 4,16 UNION ALL
SELECT 5,32 UNION ALL
SELECT 6,64 UNION ALL
SELECT 7,128
--Create table to collect the row data.
DECLARE @DeletedRecords TABLE
(
[RowLogContents] VARBINARY(8000),
[AllocUnitID] BIGINT,
[Transaction ID] NVARCHAR(Max),
[Slot ID] INT,
[FixedLengthData] SMALLINT,
[TotalNoOfCols] SMALLINT,
[NullBitMapLength] SMALLINT,
[NullBytes] VARBINARY(8000),
[TotalNoofVarCols] SMALLINT,
[ColumnOffsetArray] VARBINARY(8000),
[VarColumnStart] SMALLINT,
[NullBitMap] VARCHAR(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 0] AS [RowLogContents]
,[AllocUnitID] AS [AllocUnitID]
,[ID] AS [Transaction ID]
,[Slot ID] as [Slot ID]
--[Fixed Length Data] = Substring (RowLog content 0, Status Bit A+ Status Bit B + 1,2 bytes)
,CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) AS [FixedLengthData] --@FixedLengthData
--[TotalnoOfCols] = Substring (RowLog content 0, [Fixed Length Data] + 1,2 bytes)
,CONVERT(INT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], CONVERT(SMALLINT, CONVERT(BINARY(2)
,REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 1, 2)))) as [TotalNoOfCols]
--[NullBitMapLength]=ceiling([Total No of Columns] /8.0)
,CONVERT(INT, ceiling(CONVERT(INT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], CONVERT(SMALLINT, CONVERT(BINARY(2)
,REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 1, 2))))/8.0)) as [NullBitMapLength]
--[Null Bytes] = Substring (RowLog content 0, Status Bit A+ Status Bit B + [Fixed Length Data] +1, [NullBitMapLength] )
,SUBSTRING([RowLog Contents 0], CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 3,
CONVERT(INT, ceiling(CONVERT(INT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], CONVERT(SMALLINT, CONVERT(BINARY(2)
,REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 1, 2))))/8.0))) as [NullBytes]
--[TotalNoofVarCols] = Substring (RowLog content 0, Status Bit A+ Status Bit B + [Fixed Length Data] +1, [Null Bitmap length] + 2 )
,(CASE WHEN SUBSTRING([RowLog Contents 0], 1, 1) In (0x30,0x70) THEN
CONVERT(INT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0],
CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 3
+ CONVERT(INT, ceiling(CONVERT(INT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], CONVERT(SMALLINT, CONVERT(BINARY(2)
,REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 1, 2))))/8.0)), 2)))) ELSE null END) AS [TotalNoofVarCols]
--[ColumnOffsetArray]= Substring (RowLog content 0, Status Bit A+ Status Bit B + [Fixed Length Data] +1, [Null Bitmap length] + 2 , [TotalNoofVarCols]*2 )
,(CASE WHEN SUBSTRING([RowLog Contents 0], 1, 1) In (0x30,0x70) THEN
SUBSTRING([RowLog Contents 0]
, CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 3
+ CONVERT(INT, ceiling(CONVERT(INT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], CONVERT(SMALLINT, CONVERT(BINARY(2)
,REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 1, 2))))/8.0)) + 2
, (CASE WHEN SUBSTRING([RowLog Contents 0], 1, 1) In (0x30,0x70) THEN
CONVERT(INT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0],
CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 3
+ CONVERT(INT, ceiling(CONVERT(INT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], CONVERT(SMALLINT, CONVERT(BINARY(2)
,REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 1, 2))))/8.0)), 2)))) ELSE null END)
* 2) ELSE null END) AS [ColumnOffsetArray]
-- Variable column Start = Status Bit A+ Status Bit B + [Fixed Length Data] + [Null Bitmap length] + 2+([TotalNoofVarCols]*2)
,CASE WHEN SUBSTRING([RowLog Contents 0], 1, 1)In (0x30,0x70)
THEN (
CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 4
+ CONVERT(INT, ceiling(CONVERT(INT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], CONVERT(SMALLINT, CONVERT(BINARY(2)
,REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 1, 2))))/8.0))
+ ((CASE WHEN SUBSTRING([RowLog Contents 0], 1, 1) In (0x30,0x70) THEN
CONVERT(INT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0],
CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 3
+ CONVERT(INT, ceiling(CONVERT(INT, CONVERT(BINARY(2), REVERSE(SUBSTRING([RowLog Contents 0], CONVERT(SMALLINT, CONVERT(BINARY(2)
,REVERSE(SUBSTRING([RowLog Contents 0], 2 + 1, 2)))) + 1, 2))))/8.0)), 2)))) ELSE null END) * 2))
ELSE null End AS [VarColumnStart]
From @ModifiedRawData
),
---Use this technique to repeate the row till the no of bytes of the row.
N1 (n) AS (SELECT 1 UNION ALL SELECT 1),
N2 (n) AS (SELECT 1 FROM N1 AS X, N1 AS Y),
N3 (n) AS (SELECT 1 FROM N2 AS X, N2 AS Y),
N4 (n) AS (SELECT ROW_NUMBER() OVER(ORDER BY X.n)
FROM N3 AS X, N3 AS Y)
insert into @DeletedRecords
Select RowLogContents
,[AllocUnitID]
,[Transaction ID]
,[Slot ID]
,[FixedLengthData]
,[TotalNoOfCols]
,[NullBitMapLength]
,[NullBytes]
,[TotalNoofVarCols]
,[ColumnOffsetArray]
,[VarColumnStart]
--Get the Null value against each column (1 means null zero means not null)
,[NullBitMap]=(REPLACE(STUFF((SELECT ',' +
(CASE WHEN [ID]=0 THEN CONVERT(NVARCHAR(1),(SUBSTRING(NullBytes, n, 1) % 2)) ELSE CONVERT(NVARCHAR(1),((SUBSTRING(NullBytes, n, 1) / [Bitvalue]) % 2)) END) --as [nullBitMap]
FROM
N4 AS Nums
Join RowData AS C ON n<=NullBitMapLength
Cross Join @bitTable WHERE C.[RowLogContents]=D.[RowLogContents] ORDER BY [RowLogContents],n ASC FOR XML PATH('')),1,1,''),',',''))
FROM RowData D
CREATE TABLE [#temp_Data]
(
[FieldName] VARCHAR(MAX) COLLATE database_default NOT NULL,
[FieldValue] VARCHAR(MAX) COLLATE database_default NOT NULL,
[Rowlogcontents] VARBINARY(8000),
[Transaction ID] VARCHAR(MAX) COLLATE database_default NOT NULL,
[Slot ID] int
)
---Create common table expression and join it with the rowdata table
--to get each column details
;With CTE AS (
/*This part is for variable data columns*/
SELECT Rowlogcontents,
[Transaction ID],
[Slot ID],
NAME ,
cols.leaf_null_bit AS nullbit,
leaf_offset,
ISNULL(syscolumns.length, cols.max_length) AS [length],
cols.system_type_id,
cols.leaf_bit_position AS bitpos,
ISNULL(syscolumns.xprec, cols.precision) AS xprec,
ISNULL(syscolumns.xscale, cols.scale) AS xscale,
SUBSTRING([nullBitMap], cols.leaf_null_bit, 1) AS is_null,
--Calculate the variable column size from the variable column offset array
(CASE WHEN leaf_offset<1 and SUBSTRING([nullBitMap], cols.leaf_null_bit, 1)=0 THEN
CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE (SUBSTRING ([ColumnOffsetArray], (2 * leaf_offset*-1) - 1, 2)))) ELSE 0 END) AS [Column value Size],
---Calculate the column length
(CASE WHEN leaf_offset<1 and SUBSTRING([nullBitMap], cols.leaf_null_bit, 1)=0 THEN CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE (SUBSTRING ([ColumnOffsetArray], (2 * (leaf_offset*-1)) - 1, 2))))
- ISNULL(NULLIF(CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE (SUBSTRING ([ColumnOffsetArray], (2 * ((leaf_offset*-1) - 1)) - 1, 2)))), 0), [varColumnStart])
ELSE 0 END) AS [Column Length]
--Get the Hexa decimal value from the RowlogContent
--HexValue of the variable column=Substring([Column value Size] - [Column Length] + 1,[Column Length])
--This is the data of your column but in the Hexvalue
,CASE WHEN SUBSTRING([nullBitMap], cols.leaf_null_bit, 1)=1 THEN NULL ELSE
SUBSTRING(Rowlogcontents,((CASE WHEN leaf_offset<1 and SUBSTRING([nullBitMap], cols.leaf_null_bit, 1)=0 THEN CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE (SUBSTRING ([ColumnOffsetArray], (2 * leaf_offset*-1) - 1, 2)))) ELSE 0 END)
- ((CASE WHEN leaf_offset<1 and SUBSTRING([nullBitMap], cols.leaf_null_bit, 1)=0 THEN CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE (SUBSTRING ([ColumnOffsetArray], (2 * (leaf_offset*-1)) - 1, 2))))
- ISNULL(NULLIF(CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE (SUBSTRING ([ColumnOffsetArray], (2 * ((leaf_offset*-1) - 1)) - 1, 2)))), 0), [varColumnStart])
ELSE 0 END))) + 1,((CASE WHEN leaf_offset<1 and SUBSTRING([nullBitMap], cols.leaf_null_bit, 1)=0 THEN CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE (SUBSTRING ([ColumnOffsetArray], (2 * (leaf_offset*-1)) - 1, 2))))
- ISNULL(NULLIF(CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE (SUBSTRING ([ColumnOffsetArray], (2 * ((leaf_offset*-1) - 1)) - 1, 2)))), 0), [varColumnStart])
ELSE 0 END))) END AS hex_Value
FROM @DeletedRecords A
Inner Join sys.allocation_units allocunits On A.[AllocUnitId]=allocunits.[Allocation_Unit_Id]
INNER JOIN sys.partitions partitions ON (allocunits.type IN (1, 3)
AND partitions.hobt_id = allocunits.container_id) OR (allocunits.type = 2 AND partitions.partition_id = allocunits.container_id)
INNER 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<0
UNION
/*This part is for fixed data columns*/
SELECT Rowlogcontents,
[Transaction ID],
[Slot ID],
NAME ,
cols.leaf_null_bit AS nullbit,
leaf_offset,
ISNULL(syscolumns.length, cols.max_length) AS [length],
cols.system_type_id,
cols.leaf_bit_position AS bitpos,
ISNULL(syscolumns.xprec, cols.precision) AS xprec,
ISNULL(syscolumns.xscale, cols.scale) AS xscale,
SUBSTRING([nullBitMap], cols.leaf_null_bit, 1) AS is_null,
(SELECT TOP 1 ISNULL(SUM(CASE WHEN C.leaf_offset >1 THEN max_length ELSE 0 END),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 AS [Column value Size],
syscolumns.length AS [Column Length]
,CASE WHEN SUBSTRING([nullBitMap], cols.leaf_null_bit, 1)=1 THEN NULL ELSE
SUBSTRING
(
Rowlogcontents,(SELECT TOP 1 ISNULL(SUM(CASE WHEN C.leaf_offset >1 THEN max_length ELSE 0 END),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
,syscolumns.length) END AS hex_Value
FROM @DeletedRecords A
Inner Join sys.allocation_units allocunits ON A.[AllocUnitId]=allocunits.[Allocation_Unit_Id]
INNER JOIN sys.partitions partitions ON (allocunits.type IN (1, 3)
AND partitions.hobt_id = allocunits.container_id) OR (allocunits.type = 2 AND partitions.partition_id = allocunits.container_id)
INNER 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>0 )
--Converting data from Hexvalue to its orgional datatype.
--Implemented datatype conversion mechanism for each datatype
--Select * from sys.columns Where [object_id]=object_id('' + @SchemaName_n_TableName + '')
INSERT INTO #temp_Data
SELECT NAME,
CASE
WHEN system_type_id IN (231, 239) THEN LTRIM(RTRIM(CONVERT(NVARCHAR(max),hex_Value))) --NVARCHAR ,NCHAR
WHEN system_type_id IN (167,175) THEN LTRIM(RTRIM(CONVERT(VARCHAR(max),REPLACE(hex_Value, 0x00, 0x20)))) --VARCHAR,CHAR
WHEN system_type_id = 48 THEN CONVERT(VARCHAR(MAX), CONVERT(TINYINT, CONVERT(BINARY(1), REVERSE (hex_Value)))) --TINY INTEGER
WHEN system_type_id = 52 THEN CONVERT(VARCHAR(MAX), CONVERT(SMALLINT, CONVERT(BINARY(2), REVERSE (hex_Value)))) --SMALL INTEGER
WHEN system_type_id = 56 THEN CONVERT(VARCHAR(MAX), CONVERT(INT, CONVERT(BINARY(4), REVERSE(hex_Value)))) -- INTEGER
WHEN system_type_id = 127 THEN CONVERT(VARCHAR(MAX), CONVERT(BIGINT, CONVERT(BINARY(8), REVERSE(hex_Value))))-- BIG INTEGER
WHEN system_type_id = 61 Then CONVERT(VARCHAR(MAX),CONVERT(DATETIME,CONVERT(VARBINARY(8000),REVERSE (hex_Value))),100) --DATETIME
WHEN system_type_id =58 Then CONVERT(VARCHAR(MAX),CONVERT(SMALLDATETIME,CONVERT(VARBINARY(8000),REVERSE(hex_Value))),100) --SMALL DATETIME
WHEN system_type_id = 108 THEN CONVERT(VARCHAR(MAX),CONVERT(NUMERIC(38,20), CONVERT(VARBINARY,CONVERT(VARBINARY(1),xprec)+CONVERT(VARBINARY(1),xscale))+CONVERT(VARBINARY(1),0) + hex_Value)) --- NUMERIC
WHEN system_type_id In(60,122) THEN CONVERT(VARCHAR(MAX),Convert(MONEY,Convert(VARBINARY(8000),Reverse(hex_Value))),2) --MONEY,SMALLMONEY
WHEN system_type_id =106 THEN CONVERT(VARCHAR(MAX), CAST(CONVERT(Decimal(38,34), CONVERT(VARBINARY,Convert(VARBINARY,xprec)+CONVERT(VARBINARY,xscale))+CONVERT(VARBINARY(1),0) + hex_Value) as FLOAT)) --- DECIMAL
WHEN system_type_id = 104 THEN CONVERT(VARCHAR(MAX),CONVERT (BIT,CONVERT(BINARY(1), hex_Value)%2)) -- BIT
WHEN system_type_id =62 THEN RTRIM(LTRIM(STR(CONVERT(FLOAT,SIGN(CAST(CONVERT(VARBINARY(8000),Reverse(hex_Value)) AS BIGINT)) * (1.0 + (CAST(CONVERT(VARBINARY(8000),Reverse(hex_Value)) AS BIGINT) & 0x000FFFFFFFFFFFFF) * POWER(CAST(2 AS FLOAT), -52)) * POWER(CAST(2 AS FLOAT),((CAST(CONVERT(VARBINARY(8000),Reverse(hex_Value)) AS BIGINT) & 0x7ff0000000000000) / EXP(52 * LOG(2))-1023))),53,LEN(hex_Value)))) --- FLOAT
When system_type_id =59 THEN Left(LTRIM(STR(CAST(SIGN(CAST(Convert(VARBINARY(8000),REVERSE(hex_Value)) AS BIGINT))* (1.0 + (CAST(CONVERT(VARBINARY(8000),Reverse(hex_Value)) AS BIGINT) & 0x007FFFFF) * POWER(CAST(2 AS Real), -23)) * POWER(CAST(2 AS Real),(((CAST(CONVERT(VARBINARY(8000),Reverse(hex_Value)) AS INT) )& 0x7f800000)/ EXP(23 * LOG(2))-127))AS REAL),23,23)),8) --Real
WHEN system_type_id In (165,173) THEN (CASE WHEN CHARINDEX(0x,cast('' AS XML).value('xs:hexBinary(sql:column("hex_Value"))', 'VARBINARY(8000)')) = 0 THEN '0x' ELSE '' END) +cast('' AS XML).value('xs:hexBinary(sql:column("hex_Value"))', 'varchar(max)') -- BINARY,VARBINARY
WHEN system_type_id =36 THEN CONVERT(VARCHAR(MAX),CONVERT(UNIQUEIDENTIFIER,hex_Value)) --UNIQUEIDENTIFIER
END AS FieldValue
,[Rowlogcontents]
,[Transaction ID]
,[Slot ID]
FROM CTE ORDER BY nullbit
--Create the column name in the same order to do pivot table.
DECLARE @FieldName VARCHAR(max)
SET @FieldName = STUFF(
(
SELECT ',' + CAST(QUOTENAME([Name]) AS VARCHAR(MAX)) FROM syscolumns WHERE id=object_id('' + @SchemaName_n_TableName + '')
FOR XML PATH('')
), 1, 1, '')
--Finally did pivot table and got the data back in the same format.
--The [Update Statement] column will give you the query that you can execute in case of recovery.
SET @sql = 'SELECT ' + @FieldName + ' FROM #temp_Data
PIVOT (Min([FieldValue]) FOR FieldName IN (' + @FieldName + ')) AS pvt
ORDER BY Convert(int,[Transaction ID],Convert(int,[Slot ID]))'
EXEC sp_executesql @sql
GO
--Execute the procedure like
--Recover_Truncated_Data_Proc 'Database name''Schema.table name','Date from' ,'Date to'
--EXAMPLE #1 : FOR ALL TRUNCATED RECORDS
EXEC Recover_Truncated_Data_Proc 'testcs','dbo.Student'
GO
--EXAMPLE #2 : FOR ANY SPECIFIC DATE RANGE
EXEC Recover_Truncated_Data_Proc 'testcs','dbo.Student','2000/01/01','2012/04/08'
--It will give you the result of all Truncated records.
Explanation
Let’s go through it step by step. The process requires few easy steps:
Step-1:
The first step is to pick the truncated records using sys.fn_dblog(SQL Log)..Given below is the sample query.
SELECT LTRIM(RTRIM(Replace([Description],'Deallocated',''))) AS [PAGE ID]
,[Slot ID],[AllocUnitId]
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 (1, 3)
AND partitions.hobt_id = allocunits.container_id) OR (allocunits.type = 2
AND partitions.partition_id = allocunits.container_id)
Where object_id=object_ID('' + 'dbo.Student' + ''))
AND Operation IN ('LOP_MODIFY_ROW') AND [Context] IN ('LCX_PFS')
AND Description Like '%Deallocated%'
Step-2:
In the above sample query, the [Page ID] contains file ID and Page ID in a merge and hex format e.g ‘0001:0000005e’, where the actual data resides after truncate.So in this step we need to separate File ID and page ID than convert it into integer and enter these values in DBCC Page to get the truncated data page.
SET @Fileid=SUBSTRING(@ConsolidatedPageID,0,CHARINDEX(':',@ConsolidatedPageID)) -- Seperate File ID from Page ID
SET @hex_pageid ='0x'+ SUBSTRING(@ConsolidatedPageID,CHARINDEX(':',@ConsolidatedPageID)+1,Len(@ConsolidatedPageID)) ---Seperate the page ID
SELECT @Pageid=Convert(INT,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 substring(@hex_pageid, 1, 2) WHEN '0x' THEN 3 ELSE 0 END) AS t(pos)
INSERT INTO @temppagedata EXEC( 'DBCC PAGE(' + @DataBase_Name + ', ' + @fileid + ', ' + @pageid + ', 1) with tableresults,no_infomsgs;');
INSERT INTO @pagedata SELECT @ConsolidatedPageID,@AllocUnitID,[ParentObject],[Object],[Field] ,[Value] FROM @temppagedata
Step-3:
Now, we have truncated data in @pagedata table but in hex values and it contains the entire page data, most of the data we don’t need. So, we will filter our required data via this query. In this query we filter all the records containing ‘Memory Dump ‘in [object] column. But the issue is, we need the data from [value] column and in this column single row data is in multiple rows like.
00000000: 30001400 01000000 00000000 60940000 28000000 †0………..`…(…
00000014: 0500e002 0029002d 00530054 00440030 00300031 †…..).-.S.T.D.0.0.1
00000028: 00426f62 31†††††††††††††††††††††††††††††††††††.Bob1
But, we need to convert it like this in single row.
30001400010000000000000060940000280000000500e0020029002d00
530054004400300030003100426f6231
INSERT INTO @ModifiedRawData ([PAGE ID],[Slot ID],[AllocUnitId]
,[RowLog Contents 0_var])
SELECT [Page ID],Substring([ParentObject],CHARINDEX('Slot', [ParentObject])+4, (CHARINDEX('Offset', [ParentObject])-(CHARINDEX('Slot', [ParentObject])+4)) ) as [Slot ID]
,[AllocUnitId]
,(
SELECT REPLACE(STUFF((SELECT REPLACE(SUBSTRING([Value],CHARINDEX(':',[Value])+1,CHARINDEX('†',[Value])-CHARINDEX(':',[Value])),'†','')
--REPLACE(SUBSTRING([Value],CHARINDEX(':',[Value])+1,48),'†','')
FROM @pagedata C WHERE B.[Page ID]= C.[Page ID] And Substring(B.[ParentObject],CHARINDEX('Slot', B.[ParentObject])+4, (CHARINDEX('Offset', B.[ParentObject])-(CHARINDEX('Slot', B.[ParentObject])+4)) )=Substring(C.[ParentObject],CHARINDEX('Slot', C.[ParentObject])+4, (CHARINDEX('Offset', C.[ParentObject])-(CHARINDEX('Slot', C.[ParentObject])+4)) ) And
[Object] Like '%Memory Dump%'
FOR XML PATH('') ),1,1,'') ,' ','')
) AS [Value]
From @pagedata B
Where [Object] Like '%Memory Dump%'
Group By [Page ID],[ParentObject],[AllocUnitId]
Order By [Slot ID]
Now, we have each row record in hex format, so the rest of the step we will follow the same as in How to recover deleted data from SQl server to convert it into actual data.
Appreciate your feedback on my posts. Please do comment.
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