Tutorial for Designer/2000
and Developer/2000

### Lesson 5, page 3

1. After you have created all the entities:

• You will need to specify the cardinality. (See table 5.1 for the Oracle Cardinality Notations). Note that Oracle symbols for relationship as well as cardinality are some what different from those in your text book by Professors Hoffer, George and Valacich.

 ORACLE SYMBOL ORACLE CARDINALITY NOTATION CARDINALITY DESCRIPTION IN SIMPLE WORDS M:1 (M to 0) Mandatory Many to Optional One M:1 (0 to 0) Optional Many to Optional One M:1 (0 to M) Optional Many to Mandatory One M:1 (M to M) Mandatory Many to Mandatory One M:M (M to 0) Mandatory Many to Optional Many M:M (0 to 0) Optional Many to Optional Many 1:1 (M to 0) Mandatory One to Optional One 1:1 (0 to 0) Optional One to Optional One 1:1 (M to M) Mandatory One to Mandatory One

• For specifying the cardinality click on any of the options next to the entity icon and drag it from the left entity to the right. In this case we have chosen the M:M (O to O) relationship, i.e. the many-to-many, optional to optional relationship. For this select the following icon from the toolbar.

• Immediately, the window called "Create Relationship" will appear. (See Figure 5.9).

• Specify what you would like the relationship to be named as. Here we will type 'take' in the From prompt and 'are_taken_by' in the To prompt. (Note that you could have used names without underscore or written in upper case letters. In this case we have used underscore for clarity purposes). In other words, "Students TAKE Courses" and "Courses ARE_TAKEN_BY Students".

Figure 5.9: The Create Relationship window

2. Your E-R diagram should now look like Figure 5.10.

Figure 5.10: E-R Diagram with the Entities and their Cardinality

On to page four

Page 1, Page 2, Page 3, Page 4 / Back to the tutorial index.