Creating a table and a constraint

Hi there, having a problem working out whats needed here.

Im trying to create a table, this table is allowed to be null, but if its not then it must meet some other criteria. I know basically what im doing but cant geta few things im trying todo. So far ive got:

CREATE TABLE SystemUsers ( Staff_id char (3) CONSTRAINT pk_SU Primary Key ( Staff_id), Manager_id char (3)
now need it so, if a value has been entered into Manager_id it must match a value in Staff_id.

Havent got a clue how to go about this? Cant find this specific thing in my book either. Any help is apreciated Received on Fri Mar 26 2004 - 03:18:02 CST