How to make CONSTRAINT CHECK for values in another table?

[TheBugSlayer]

Is it possible to set a constraint on a field so that it checks that the value being entered exists in another table?

Something like
... emp_id empid
CONSTRAINT CK_emp_id CHECK (emp_id IN
SELECT emp_id FROM Employees)...

It that is not possible, what is the alternative?

Thanks for your help.

 

[SQLSister]

You could use an instead of trigger. PUt the thing in an if and run the update only if it doesn;t exist inthe other table

 

[TheBugSlayer]

Yes that works, I know for sure. I think I took the wrong aproach from start, what I need is to add a foreign key constraint to the field.

Thank you anyway.