Auditing and synchronising data in cross database using a trigger

Auditing and synchronising tables in different databases, with different data structure using a trigger

About

This is a very stripped down version of some code that we set up at a previous client site. They had two very different databases on different servers (customer and dialler) that needed to have certain data syncronised in real time.

There were a couple of ways of doing it, replication, or stored procedures linked to a job or triggers, in their example it had to be a job, because we didn't own the source code for one of the databases, however my preferred method would be using triggers with something like this...

SQL

USE ClaytabaseAcadamyGOCREATE TABLE Customer(CustomerID INT IDENTITY(1,1) CONSTRAINT PK_CustomerID PRIMARY KEY,CustomerName NVARCHAR(100),CustomerStatus INT--,Other Customer Data...)CREATE TABLE CustomerAudit(CustomerAuditID INT IDENTITY(1,1) CONSTRAINT PK_CustomerAuditID PRIMARY KEY,CustomerAuditType NVARCHAR(100),CustomerAuditDate DATETIME DEFAULT GETDATE(),CustomerID INT,CustomerName NVARCHAR(100),CustomerStatus INT)     CREATE TABLE Dialler(CustomerID INT CONSTRAINT PK_DiallerCustomerID PRIMARY KEY,CustomerStatus INT,CustomerName NVARCHAR(100),DiallerStatus INT--Other Dialler Records)GO

So now we have created some very basic tables that can store customer data. Next we will create some Stored Procedures to handle updating records on the dialler side.

The reason I have done this as stored procedures is to keep the volume of data down (i don't want server 1 sending database records to server 2), it is in effect pinching what would normally be done in a web environment.

SQL

USE ClaytabaseAcadamyGOCREATE PROC DiallerUpdate(@CustomerID INT,@CustomerName NVARCHAR(100),@CustomerStatus INT) AS BEGINUPDATE Dialler SET CustomerStatus=@CustomerStatus,CustomerName=@CustomerNameWHERE CustomerID=@CustomerIDENDGOCREATE PROC DiallerInsert(@CustomerID INT,@CustomerName NVARCHAR(100),@CustomerStatus INT) AS BEGININSERT INTO Dialler(CustomerID,CustomerName,CustomerStatus,DiallerStatus)SELECT @CustomerID,@CustomerName,@CustomerStatus,0ENDGOCREATE PROC DiallerDelete(@CustomerID INT) AS BEGINDELETE FROM DiallerWHERE CustomerID=@CustomerIDENDGO

Now we have created these, we can move onto creating a trigger that will handle sending the data and as we are doing it, we can also auditing our records.

SQL

USE ClaytabaseAcadamyGOCREATE TRIGGER CustomerInsert ON Customer AFTER INSERTAS BEGINDECLARE @CustomerID INT,@CustomerName NVARCHAR(100),@CustomerStatus INT--Get Record DetailsSELECT @CustomerID=CustomerID,@CustomerName=CustomerName,@CustomerStatus=CustomerStatus FROM inserted--Add to AuditINSERT INTO CustomerAudit(CustomerAuditType,CustomerID,CustomerName,CustomerStatus)SELECT 'Record Created',@CustomerID,@CustomerName,@CustomerStatus--Call Insert ProcedureEXEC dbo.DiallerInsert @CustomerID,@CustomerName,@CustomerStatusENDGOCREATE TRIGGER CustomerUpdate ON Customer AFTER UpdateAS BEGINDECLARE @CustomerID INT,@CustomerName NVARCHAR(100),@CustomerStatus INT--Get Record DetailsSELECT @CustomerID=CustomerID,@CustomerName=CustomerName,@CustomerStatus=CustomerStatus FROM inserted--Add to AuditINSERT INTO CustomerAudit(CustomerAuditType,CustomerID,CustomerName,CustomerStatus)SELECT 'Record Updated',@CustomerID,@CustomerName,@CustomerStatus--Call Update ProcedureEXEC dbo.DiallerUpdate @CustomerID,@CustomerName,@CustomerStatusENDGO CREATE TRIGGER CustomerDelete ON Customer AFTER DELETEAS BEGINDECLARE @CustomerID INT,@CustomerName NVARCHAR(100),@CustomerStatus INT--Get Record DetailsSELECT @CustomerID=CustomerID,@CustomerName=CustomerName,@CustomerStatus=CustomerStatus FROM deleted--Add to AuditINSERT INTO CustomerAudit(CustomerAuditType,CustomerID,CustomerName,CustomerStatus)SELECT 'Record Deleted',@CustomerID,@CustomerName,@CustomerStatus--Call Delete ProcedureEXEC dbo.DiallerDelete @CustomerIDENDGO

And that is pretty much it, we now have an audit of data, and the records on both sides will be syncrised within milliseconds... If it needs to be done cross server, change the EXEC command to {servername}.{databasename}.{schema}.DiallerDelete etc/

Here we can test it.

SQL

USE ClaytabaseAcadamyGO--Insert DataINSERT INTO Customer(CustomerName,CustomerStatus) SELECT ' Name 1',0INSERT INTO Customer(CustomerName,CustomerStatus) SELECT ' Name 2',0INSERT INTO Customer(CustomerName,CustomerStatus) SELECT ' Name 3',0UPDATE Customer SET CustomerStatus=2 WHERE CustomerID=1UPDATE Customer SET CustomerName=' Name 4' WHERE CustomerID=2DELETE FROM Customer WHERE CustomerID=3--Review DataSELECT * FROM DiallerSELECT * FROM CustomerSELECT * FROM CustomerAudit

Selecting from the tables you can now check that each process has done it's job properly. by creating the different processes, it has also allowed us to be a lot more creative with what we have done.

Results

Dialler Records CustomerID CustomerStatus CustomerName DiallerStatus 1 2 Name 1 0 2 0 Name 4 0 Customer Records CustomerID CustomerName CustomerStatus 1 Name 1 2 2 Name 4 0 Audit Records CustomerAuditID CustomerAuditType CustomerID CustomerName CustomerStatus 1 Record Created 1 Name 1 0 2 Record Created 2 Name 2 0 3 Record Created 3 Name 3 0 4 Record Updated 1 Name 1 2 5 Record Updated 2 Name 4 0 6 Record Deleted 3 Name 3 0

Dialler Records
CustomerID	CustomerStatus	CustomerName	DiallerStatus
1	2	Name 1	0
2	0	Name 4	0

Customer Records
CustomerID	CustomerName	CustomerStatus
1	Name 1	2
2	Name 4	0

Audit Records
CustomerAuditID	CustomerAuditType	CustomerID	CustomerName	CustomerStatus
1	Record Created	1	Name 1	0
2	Record Created	2	Name 2	0
3	Record Created	3	Name 3	0
4	Record Updated	1	Name 1	2
5	Record Updated	2	Name 4	0
6	Record Deleted	3	Name 3	0