Modify an existing constraint

Modify an existing constraint requires next steps

- drop the existing constraint

ALTER TABLE [dbo].[tblA] 

DROP FK_tblA_a

-adding this constraint again 

ALTER TABLE [dbo].[tblA]  WITH CHECK ADD  CONSTRAINT [FK_tblA_a] FOREIGN KEY([IdCol])

REFERENCES [dbo].[tblB] ([ID])

ON UPDATE CASCADE

ON DELETE CASCADE