Database Reference
In-Depth Information
Figure 2.26
Conigure cardinality.
2.
Creating nonidentifying relationship
: In the class registration data model, there are
several nonidentifying relationships: Course-Class, Course-Prerequisite, Weekday-
Class, Time Block-Class, Semester-Class, and Faculty-Student. he following steps
show you how to create a nonidentifying relationship between the entities COURSE
and CLASS.
◾
Assume that both COURSE and CLASS in Figure 2.15 have been created. Click
Connector Tool
on the tool bar. Move the mouse cursor over the parent entity
COURSE
. When a red rectangle appears, press the mouse. hen, hold the mouse
and move the cursor over to the child entity
CLASS
. When a red rectangle appears
around the child entity, release the mouse. A nonidentifying relationship connec-
tor is automatically drawn from the parent entity to the child entity.
◾
If a diamond icon appears on the relationship connector line near the COURSE
side, it means that a course is optional. In our data model, a course is required
for a class. To ix the problem, right click
CLASS
entity and select
Database
Properties
. Select
Columns
in the
Categories
pane. Make the column
CourseId
required by checking the
Req'd
option as shown in Figure 2.27. he diamond
icon should disappear.
◾
To specify the cardinality, double click the newly created relationship connector line.
In the
Database Properties
dialog, select
Miscellaneous
in the
Categories
pane.
Check the
One or more
option. You should have the result shown in Figure 2.15.
Figure 2.27
Conigure required attributes.
