Foreign key relationship with composite primary keys in SQL Server 2005

Question

I have two tables Table1(FileID,BundledFileID,Domain) and Table2(FileID,FileType,FileName).

In Table2 FileID and FileType are the composite primary key. I want to create a foreign key relationship from Table1.FileID to Table2. Is it possible to do this? Then how plz help.

I am using SQL Server 2005

Answer 1

Since Table2 has a composite primary key (FileID, FileType), then any reference to it must also include both columns.

ALTER TABLE dbo.Table1
  ADD CONSTRAINT FK_Table1_Table2
  FOREIGN KEY(FileID, FileType) REFERENCES Table2(FileID, FileType)

Unless you have a unique constraint/index on the Table2.FileID field (but if so: why isn't this the PK??), you cannot create a FK relationship to only parts of the PK on the target table - just can't do it.

Answer 2

marc has already given a pretty good answer. If the rows in Table1 only ever relate to one type of File (e.g. FileType 'ABC'), then you can add FileType to Table1 as a computed column:

ALTER TABLE Table1 ADD FileType as 'ABC'

Which you can then use in the Foreign Key.