How do i drop a foreign key constraint if it exists in sql server 2005?

Question

I can drop a table if it exists using the following code but do not know how to do the same with a constraint:

IF EXISTS(SELECT 1 FROM sys.objects WHERE OBJECT_ID = OBJECT_ID(N'TableName') AND type = (N'U')) DROP TABLE TableName
go

I also add the constraint using this code:

ALTER TABLE [dbo].[TableName] 
  WITH CHECK ADD CONSTRAINT [FK_TableName_TableName2] FOREIGN KEY([FK_Name])
    REFERENCES [dbo].[TableName2] ([ID])
go

Answer 1

IF EXISTS (SELECT * FROM sys.foreign_keys WHERE object_id = OBJECT_ID(N'dbo.FK_TableName_TableName2') AND parent_object_id = OBJECT_ID(N'dbo.TableName'))

ALTER TABLE [dbo.TableName] DROP CONSTRAINT [FK_TableName_TableName2]

Answer 2

ALTER TABLE [dbo].[TableName]
    DROP CONSTRAINT FK_TableName_TableName2