How do you effectively model inheritance in a database?

Question

What are the best practices for modeling inheritance in databases?

What are the trade-offs (e.g. queriability)?

(I\'m most interested in SQL Server and .NET,

Answer 1

Using SQL ALchemy (Python ORM), you can do two types of inheritance.

The one I've had experience is using a singe-table, and having a discriminant column. For instances, a Sheep database (no joke!) stored all Sheep in the one table, and Rams and Ewes were handled using a gender column in that table.

Thus, you can query for all Sheep, and get all Sheep. Or you can query by Ram only, and it will only get Rams. You can also do things like have a relation that can only be a Ram (ie, the Sire of a Sheep), and so on.