--CELKO-- (jcelko212_at_earthlink.net) writes:
> CREATE TABLE Vehicles
> (vin CHAR(17) NOT NULL PRIMARY KEY,
> vehicle_type CHAR(3) NOT NULL
> CHECK(vehicle_type IN ('SUV', 'SED')),
> UNIQUE (vin, vehicle_type),
> ..);
>
> Notice the overlapping candidate keys. I then use a compound candidate
> key (vin, vehicle_type) and a constraint in each sub-class table to
> assure that the vehicle_type is locked and agrees with the Vehicles
> table. Add some DRI actions and you are done:
Ah! Interesting trick! I'll save a mental note about that.
--
Erland Sommarskog, SQL Server MVP, sommar_at_algonet.se
Books Online for SQL Server SP3 at
http://www.microsoft.com/sql/techinfo/productdoc/2000/books.asp
Received on Sat May 29 2004 - 17:05:37 CDT
