Skip to main content

DDL Triggers

We had a request from a developer who wanted to access data from a source database and another database on the same server. We needed to ensure that the underlying tables are not changed in a way that would impact on the view in either database

Prior to 2005 I would have to have done this using a myriad of views and the schemabinding option. Since SQL Server 2005 you can use DDL triggers to fire when certain DDL statements, like CREATE TABLE, ALTER TABLE, DROP TABLE are fired.

DDL triggers focus on changes to the definition of the database schema/object rather than actual data. DDL triggers can be scoped at database level and server level. The server scoped triggers apply to server objects such as logins and the former are database scoped and apply to database objects such as tables and indexes. The following trigger fires for every DROP TABLE or ALTER TABLE execution and stops any table changes being made without first disabling the trigger.





PRINT 'You must disable Trigger "safety" to drop or alter tables!'


Some may find this a little restrictive and may like to tie the trigger down to a particular table or object...This takes a little more invention:


FOR alter_table





SET @ObjectName = 'DDL_Test'

DECLARE @object nvarchar(100)

SET @object = @data.value('(/EVENT_INSTANCE/ObjectName)[1]','nvarchar(100)')

PRINT 'Altering object :' + @object

IF @Object = @ObjectName


PRINT 'Alter schema not allowed on this database - disable the DDL trigger'



In the above statement the trigger fires for each ALTER statement BUT it will only rollback the DDL statement if it includes the object specified.


Popular posts from this blog

SQL Server 2012 and Virtual Service Accounts

This post is written by David Postlethwaite
If you are using SQL Server 2012 you will probably have noticed that the default account for the SQL services has changed from that used in previous versions. With SQL 2005 and 2008 the default account for SQL service and SQL Agent service was “NT Authority\System”. This is one the built in accounts on a Windows machine, managed by the machine and selectable from a dedicated dropdown list

The Network Service account was introduced in Windows 2003 as an alternative to using the LocalSystem account, which has full local system privileges on the local machine, a major security concern.
The Network Service has limited local privileges easing these security concerns but when many services on a machine use the Network Service account it becomes harder to track which service is actually accessing resources and performing actions, because all the services are using the one Network Service account.
Also, this account, by default, has sysadmin per…

Always Encrypted

By David Postlethwaite

Always Encrypted is new features in SQL Server 2016 and it is also available in Azure SQL Database. Here you can encrypt columns in a table with a master key and a certificate so that they will appear as encrypted strings to those who don’t have the required certificate installed on their pc.
Once the certificate is installed on the computer then the unencrypted data can then be seen as normal.

The data passes from database to your application as the encrypted value, only the application with the correct certificate can unencrypt the data so it is secure across the wire. This will go some way to resolving the concern of people worried about putting their sensitive data on a shared server in the cloud such as Microsoft Azure and accessing the data across the Internet.

At the time of writing Always Encrypted is only supported with ADO.NET 4.6, JDBC 6.0 and ODBC 13.1 but expect other driver to become available.

The calling application (including SSMS) must also hav…

How to Setup Kerberos Correctly

David was in Copenhagen this weekend delivering his Kerberos talk Taming the Beast: Kerberos for the SQL DBA to SQL Saturday Denmark. I have had a quick chat with him via email since he got back and he said he had a great time. The event was very well attended with 280+ attendees and his talk was well attended.

I think David is planning submitting a few sessions to SQL Saturday events in Europe in the next few months so look out for him there and we'll keep you posted as to his whereabouts when schedules get finalised later in the year.

David has pre-recorded his Kerberos talk. You can watch on you tube and I have also embedded it in this post if you want to see what his kerberos talk  covers...

If we can help you with a SQL Sever problem visit our SQL Server Consulting page or contact us