What alternatives exist when a table requires too many foreign keys? We have a base table that defines parts and holds information like part number, description, price, weight, etc.  We also have approximately 400 tables that reference the base table and provide additional information about the parts based on their type / category.

We started by using foreign key constraints so that a part cannot be deleted from the base table if it is being referenced in one of the 400 part specific tables but we quickly reached the maximum 253 recommended foreign keys for SQL Server 2005.

Are there any alternatives to foreign keys in this situation that will ensure data integrity?  We haven't seen performance issues when accessing the data but updating an existing part in the base table will fail as the query plan is too complex.
If there's any way to group parts, you might be able to introduce intermediate tables as a workaround.  This won't work.

Parts
+ Table 1
+ Table 2
+ ...
+ Table 400


But something along these lines might.

Parts
+ RedOrangeYellow parts
  + Table 1
  + Table 2
  + ...
  + Table 200

+ GreenBlueIndigoViolet parts
  + Table 201
  + Table 202
  + ...
  + Table 400


I'd want to take a hard look at your DDL before I recommended doing this, though.  And if you do this, don't start throwing ID numbers all over the place. You ought to be able to join "Table 400" directly to "Parts" without including "GreenBlueIndigoViolet parts".