What is the purpose of including CHECK CONSTRAINT & GO in the generated database schema script

Question

I am working on SDL Server 2008 R2, where I generated a schema-only database script. The generated script is as follows:

ALTER TABLE [dbo].[ConsoleServer]  WITH CHECK ADD  CONSTRAINT [FK_ConsoleServer_RackUnits] FOREIGN KEY([RackUnitID])
REFERENCES [dbo].[RackUnits] ([UnitID])
GO
ALTER TABLE [dbo].[ConsoleServer] CHECK CONSTRAINT [FK_ConsoleServer_RackUnits]

I have these 2 questions:-

• I know that the first line is responsible to create a FK between two DB tables. but what is the purpose of the following :

  ALTER TABLE [dbo].[ConsoleServer] CHECK CONSTRAINT [FK_ConsoleServer_RackUnits]

• In general, why does the DB script have the word GO. Now if I remove it the script will be executed well on the destination DB, so why it is included in the script prior to any statement?

Answer 1

1. The ALTER TABLE ... CHECK CONSTRAINT ... line enables the constraint. You can add a constraint and leave it disable (while you clean up the data for example). See more here

2. GO is a batch separator, it's only recognized by SSMS. Some statements, such as CREATE PROCEDURE... requires it to be the first statement in the batch. You can type it out in a new file, or use GO to terminate the previous batch. Don't send GO from your application through OLEDB or ADO.NET though.