Databases Reference
In-Depth Information
When developers need a user to select an employee with this model, they may decide to use two
items rather than one to help simplify the selection process, as shown in Figure 11-24. This is known as a
cascading list of values (LOV).
Figure 11-24.
Example of one-to-many cascading select lists
The default functionality for cascading LOVs is such that when the parent value is changed, the
child values are replaced with new values that reflect the new parent value. If a child value had been
selected prior to the refresh then the selection would have been lost.
When the relationship is one to many, the default functionality for cascading LOVs works fine
because any selected value will not exist in the new set of values. But sometimes the relationship can be
many to many, for example, movies to actors (shown in Figure 11-25). With this type of relationship it's
possible for a user to select different movies which have overlapping actors (think of the Indiana Jones
series and Harrison Ford).
Figure 11-25.
Many-to-many relationship
Even with such a change in the data model, the cascading select lists could appear the same as
before, as in Figure 11-26.
