Change Data Capture (CDC) in SQL Server 2008

Recently I was working on one project and client required to audit the data, means, insert / update / delete should be tracked on some important table. There are many ways you can capture these information (Audit Trail), I have written quite a few articles on this subject too but all those needs additional code to be written. Fortunately my client is using SQL Server 2008 R2 version so I don’t even need to write down any specific code to capture changed data as there is facility of CDC (Change Data capture) in SQL Server 2008.

Even before we look at CDC in details, make sure you have your SQL Server Agent is running as CDC in SQL Server 2008 will use SQL Server Agent to make audit trail for you. If your SQL Server Agent is not running at the moment, start it from control Panel->Administrative Tools-> Services. You can find “SQL Server Agent (YourInstanceName)”, just start this service and then you will be able to work on CDC.

create database SQLHub

GO

use SQLHub

go

Create Table ChangeDataCapture

(

      ID INT Identity(1,1)

      ,Name varchar(20)

)

GO

--enable CDC in SQLHub database

--this will create "cdc" schema in SQLhub database too

--along with "cdc" schema, it will create some system table

--in "cdc" schema

USE SQLHub

GO

EXEC sys.sp_cdc_enable_db

GO

--now enable CDC for our table created above.

--when you will enable cdc for ChangeDataCapture table

--it will create two job under SQL Server Agent

--which will read data from transaction whenever you will make any change in data

--and stores it in CDC table

USE SQLHub

GO

EXEC sys.sp_cdc_enable_table

@source_schema = N'dbo',

@source_name   = N'ChangeDataCapture',

@role_name     = NULL

GO

--now you have orginal table, named "ChangeDataCapture"

--another table to keep all changes "ChangeDataCapture",

--which has been created in step above

select * from ChangeDataCapture

--following table will be there under category of "System Tables" folder.

select * from cdc.dbo_ChangeDataCapture_CT

--now let us make some DML operation in ChangeDataCapture table and

--observe how does it stores data in cdc.dbo_ChangeDataCapture_CT

INSERT INTO ChangeDataCapture

SELECT 'Ritesh Shah' UNION ALL

SELECT 'Rajan Shah' UNION ALL

SELECT 'Teerth Shah'

GO

--see the data in both tables

select * from ChangeDataCapture

--in cdc.dbo_ChangeDataCapture_CT, you can see value 2 in _$operation field.

--2 represent INSERT.

select * from cdc.dbo_ChangeDataCapture_CT

--see effect of UPDATE now.

UPDATE ChangeDataCapture

SET Name='Rajan Jain' WHERE Name='Rajan Shah'

--see the data in both tables

select * from ChangeDataCapture

--in cdc.dbo_ChangeDataCapture_CT, you can see value 3 and 4 in _$operation field.

--3 represent value before UPdate and 4 represent new value after update.

select * from cdc.dbo_ChangeDataCapture_CT

--see effect of DELETE now

Delete From ChangeDataCapture WHERE ID=2

GO

--see the data in both tables

select * from ChangeDataCapture

--in cdc.dbo_ChangeDataCapture_CT, you can see value 1 in _$operation field.

--1 represent DELETE operation

select * from cdc.dbo_ChangeDataCapture_CT

BTW, if you wish to look at the other manual method of capturing table tracking as known as Audit Trail, have a look at following links:

http://www.sqlhub.com/2011/07/audit-trail-with-output-clause-in-sql.html

http://www.sqlhub.com/2009/03/auditing-trail-with-trigger-in-sql.html

http://www.sqlhub.com/2009/11/audit-in-sql-server-2008.html

http://www.sqlhub.com/2009/08/output-clause-in-sql-server-20082005.html

http://www.sqlhub.com/2009/03/keep-log-of-update-in-same-table-with.html

Reference: Ritesh Shah

http://www.sqlhub.com
Note: Microsoft Books online is a default reference of all articles but examples and explanations prepared by Ritesh Shah, founder of http://www.SQLHub.com

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