What is the most portable way to check whether a trigger exists in SQL Server?

StackOverflow https://stackoverflow.com/questions/636452

Question

I'm looking for the most portable method to check for existence of a trigger in MS SQL Server. It needs to work on at least SQL Server 2000, 2005 and preferably 2008.

The information does not appear to be in INFORMATION_SCHEMA, but if it is in there somewhere, I would prefer to use it from there.

I do know of this method:

if exists (
    select * from dbo.sysobjects 
    where name = 'MyTrigger' 
    and OBJECTPROPERTY(id, 'IsTrigger') = 1
) 
begin

end

But I'm not sure whether it works on all SQL Server versions.

Was it helpful?

Solution

This works on SQL Server 2000 and above

IF OBJECTPROPERTY(OBJECT_ID('{your_trigger}'), 'IsTrigger') = 1
BEGIN
    ...
END

Note that the naive converse doesn't work reliably:

-- This doesn't work for checking for absense
IF OBJECTPROPERTY(OBJECT_ID('{your_trigger}'), 'IsTrigger') <> 1
BEGIN
    ...
END

...because if the object doesn't exist at all, OBJECTPROPERTY returns NULL, and NULL is (of course) not <> 1 (or anything else).

On SQL Server 2005 or later, you could use COALESCE to deal with that, but if you need to support SQL Server 2000, you'll have to structure your statement to deal with the three possible return values: NULL (the object doesn't exist at all), 0 (it exists but is not a trigger), or 1 (it's a trigger).

OTHER TIPS

There's also the preferred "sys.triggers" catalog view:

select * from sys.triggers where name = 'MyTrigger'

or call the sp_Helptrigger stored proc:

exec sp_helptrigger 'MyTableName'

But other than that, I guess that's about it :-)

Marc

Update (for Jakub Januszkiewicz):

If you need to include the schema information, you could also do something like this:

SELECT
    (list of columns)
FROM sys.triggers tr
INNER JOIN sys.tables t ON tr.parent_id = t.object_id
WHERE t.schema_id = SCHEMA_ID('dbo')   -- or whatever you need

Assuming it is a DML trigger:

IF OBJECT_ID('your_trigger', 'TR') IS NOT NULL
BEGIN
    PRINT 'Trigger exists'
END
ELSE
BEGIN
    PRINT 'Trigger does not exist'
END

For other types of objects (tables, views, keys, whatever...), see: http://msdn.microsoft.com/en-us/library/ms190324.aspx under 'type'.

Tested and doesn't work on SQL Server 2000:

select * from sys.triggers where name = 'MyTrigger'

Tested and works ok on SQL Server 2000 and SQL Server 2005:

select * from dbo.sysobjects
where name = 'MyTrigger' and OBJECTPROPERTY(id, 'IsTrigger')

In addition to the excellent answer by marc_s:

if the existence check is intended prior to dropping or modifying the trigger in some way, use a direct TSQL try/Catch bock, as the fastest means.

For instance:

BEGIN TRY
    DROP TRIGGER MyTableAfterUpdate;
END TRY
BEGIN CATCH
    SELECT ERROR_NUMBER() AS erno WHERE erno = 3701; -- may differ in SQL Server < 2005
END CATCH;

The Error Message will be

Cannot drop the trigger 'MyTableAfterUpdate', because it does not exist or you do not have permission.

Then simply check if the Executed Result returned rows or not, which is easy in direct sql as well as the programmatic APIs (C#,...).

Are trigger names forced to be unique in SQL server?

As triggers are by definition applied to a specific table would it not be more efficient to restrict the search to only the table in question?

We have a database with over 30k tables in it all of which have at least one trigger and may have more (bad DB design - quite probably, but it made sense years ago and didn't scale well)

I use

SELECT * FROM sys.triggers 
WHERE [parent_id] = OBJECT_ID(@tableName) 
AND [name] = @triggerName

I would use this syntax to check and drop trigger

IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[SCHEMA_NAME].[TRIGGER_NAME]') AND type in (N'TR'))
DROP TRIGGER [SCHEMA_NAME].[TRIGGER_NAME]

If you're trying to find a server scoped DDL Trigger on SQL Server 2014, you should try sys.server_triggers.

IF EXISTS (SELECT * FROM sys.server_triggers WHERE name = 'your trigger name')
BEGIN
    {do whatever you want here}
END

If I told tou anything incorrect, please let me know.

Edit: I didn't check for this dm on another versions of SQL Server.

Generated by Sql Server Management Studio:

IF  EXISTS (SELECT * FROM sys.triggers WHERE object_id = OBJECT_ID(N'[dbo].[RolesYAccesos2016_UsuariosCRM_trgAfterInsert]'))
DROP TRIGGER [dbo].[RolesYAccesos2016_UsuariosCRM_trgAfterInsert]
GO


CREATE TRIGGER [dbo].[RolesYAccesos2016_UsuariosCRM_trgAfterInsert] 
ON  [PortalMediadores].[dbo].[RolesYAccesos2016.UsuariosCRM]
FOR INSERT
AS  
...

For select @@version

Microsoft SQL Server 2008 R2 (RTM) - 10.50.1797.0 (X64) Jun 1 2011 15:43:18 Copyright (c) Microsoft Corporation Enterprise Edition (64-bit) on Windows NT 6.1 (Build 7601: Service Pack 1) (Hypervisor)

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