What is the best way to represent a relationship where
an item of type A is associated with exactly one item
of type B or C or D. For example, consider a "best
friend" relationship and suppose a person's best friend
could be another person, a dog, or a computer.
My inclination is to start with three tables (pardon my
attempt at sql):
CREATE TABLE Person(
id INTEGER NOT NULL PRIMARY KEY,
name CHAR(10) NOT NULL);
CREATE TABLE Computer(
id INTEGER NOT NULL PRIMARY KEY,
brand CHAR(10) NOT NULL,
speed INTEGER NOT NULL);
CREATE TABLE Dog(
id INTEGER NOT NULL PRIMARY KEY,
name CHAR(10) NOT NULL,
breed CHAR(10) NOT NULL);
What's the best way to augment this to include the
"best-friend" relation?
