A Mapping dissected
option
topping
id
(FK) color
Option
Topping
∙
color
∙
id
∙
name
∙
aspect
Shape
id
name
kind
aspect
Topping
∙
id
∙
name
--------------
∙
color
Topping instance
Rows of same key, kind=1
B
C
A
3 Parts to mapping
:
B
base class mapping
A
topping table for Topping
C option table for Topping
Together, 2-way mapping
(null)
25