Database Reference
In-Depth Information
The foregoing strategies should underscore forcefully in your mind, the importance
of foreign keys in database design. In fact, foreign keys are referred to as the “glue” that
holds the database together. We shall revisit this concept in the next chapter.
In many textbooks and database environment, you will see and/or hear the
term
parent-child relationship
. This is a rather lame term, borrowed from preexisting
hierarchical database systems, to describe 1:1 and 1:M relationships. In a parent-child
relationship, the
parent relation
is the referenced relation; the child relation is the
referencing relation
. Throughout this course, these terms are avoided because they are
rather confusing, and do not accurately describe several scenarios involving 1:1 and/or
1:M relationships. Alternately, we will use no euphemism for 1:1 and 1:M relationships;
instead of parent relation, we'll say the
referenced relation
; instead of child relation, we
say
primary relation
or
referencing relation
.
Figure 3-10.
Implementing M:M Relationships
