How to add “IF NOT EXISTS” to create trigger statement

Question

I am using sql server 2008 R2. More specifically, Microsoft SQL Server 2008 R2 (RTM) - 10.50.1600.1 (X64) Apr 2 2010 15:48:46 Copyright (c) Microsoft Corporation Stan

Answer 1

As other answers above not mentioned an important point I wrote this answer:

• When we want to find a trigger or another object in sys.objects table, it is better to check accurately (with schema or object_id, etc) in where clause to avoid same name invalid results. Consider when another trigger with the same name already exists in another schema... Therefore, because the sys.object table contains an schema_id column, we can use it in addition to name and type columns to query more accurately as I provided as example below.

• As Microsoft docs mentioned here under "Trigger Limitations":

CREATE TRIGGER must be the first statement in the batch and can apply to only one table.

therefore we use EXECUTE to overcome this limitation:

IF NOT EXISTS (select * from sys.objects where schema_id=SCHEMA_ID('dbo') AND type='TR' and name='Insert_WithdrawalCodes')
BEGIN
   EXECUTE ('CREATE TRIGGER [Insert_WithdrawalCodes] ON [dbo].[PupilWithdrawalReason]
   AFTER INSERT
   AS 
   BEGIN
      SET NOCOUNT ON;
      ...
   END');
END