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

repeat of similar thread answer

in O-R mapping, inheritance maps to a parent table where the parent and child tables use the same identifier

for example

create table Object (
    Id int NOT NULL --primary key, auto-increment
    Name varchar(32)
)
create table SubObject (
    Id int NOT NULL  --primary key and also foreign key to Object
    Description varchar(32)
)

SubObject has a foreign-key relationship to Object. when you create a SubObject row, you must first create an Object row and use the Id in both rows

EDIT: if you're looking to model behavior also, you would need a Type table that listed the inheritance relationships between tables, and specified the assembly and class name that implemented each table's behavior

seems like overkill, but that all depends on what you want to use it for!