SQL Server：此sql语句是什么意思

Question

I've been comparing databases using vs 2010 scheme comparing tool and it generated some stuff which is not clear. For example at the end of the script it has this statement:

ALTER TABLE [dbo].[My_table] WITH CHECK CHECK CONSTRAINT [FK_FOREIGN_ID];

Can anyone explain what this means?

Answer 1

It means that existing data should be checked against the constraint when it is added.

Failure to have the CHECK CHECK leaves your constraints untrusted and they cannot be used by the query optimiser.

Answer 2

That tells SQL Server to validate the constraint against new rows. The counter example would be to use WITH NOCHECK to temporarily disable validation checks for new rows.

ALTER TABLE (Transact-SQL) (WITH CHECK | WITH NOCHECK )