Sub-Entities

When creating sub-entities should you put a column in the root table saying what kind of sub-entity it is, or is the presence of a row in the more specific table? For example:

CREATE TABLE dbo.Clients
(

ClientIdentifier varchar(20) NOT NULL PRIMARY KEY )

CREATE TABLE dbo.Individuals
(

ClientIdentifier varchar(20) NOT NULL PRIMARY KEY REFERENCES dbo.Clients ( ClientIdentifier ),
NameTitleCode varchar(12) NOT NULL,
GivenName varchar(40) NOT NULL,
FamilyName varchar(40) NOT NULL
)

CREATE TABLE dbo.Organizations
(

ClientIdentifier varchar(20) NOT NULL PRIMARY KEY REFERENCES dbo.Clients ( ClientIdentifier ),
OrganizationName varchar(200) NOT NULL
)

What is the best way to force a client to only be an individual OR an organization? Trigger? Received on Fri Jul 01 2005 - 21:57:42 CDT