Tutorial for Designer/2000
Lesson 5, page 4
- The next step will be to create the attributes for the various entities. In order to do that:
- Right-click on the Student entity and click on Properties. (See Figure 5.11).
Figure 5.11: Selecting the properties of the Student entity
- You will immediately see the Edit Entity window. (See Figure 5.12).
Figure 5.12: The Edit Entity window
- Then select the attributes tab. The attributes window will appear with the various columns such as Name, Domain (not null or null), Format (whether varchar2, number, etc.), maxLength, primary (whether it is a Primary Key or not). The attributes that you will create for STUDENT are: STUDID (primary), STUDNAME, FTPT_STATUS, MAJOR, SEX, START_SEM, and START_YEAR). Fill in the Format, MaxLen and Primary fields as shown in Figure 5.13, and click Apply or OK.
Figure 5.13: The Attributes window for the Student entity
- Similarly, using step 9 create the attributes COURSEID(primary), COURSENAME, SCHEDULE and MAXCLASS_SIZE for the COURSE entity and click OK. (See Figure 5.14).
Figure 5.14: The Attributes window for the Course entity
- The attributes will be shown on the entity. (See Figure 5.15). (The # sign to the left of an attribute indicates that the attribute is the identifier/key for the entity).
Figure 5.15: The completed E-R diagram
You have now successfully created your first simple E-R diagram.
- Save your work by File Save Diagram As ERDSRS . DO NOT EXIT OUT OF THE E-R DIAGRAMMER.
Some Additional Conventions in Oracle Designer/2000
- Attributes do not appear as ellipses connected to the entity by a line but appear as text within the rounded rectangle representing the entity (see below).
- Relationships are not represented using a diamond.
- Subtypes are not represented using the ISA relationship but by creating entities that are subtypes within the box representing the supertype.
In this lesson you learned:
- To create entities
- Create and name the attributes and specify their properties
- Specify the relationships between the entities and define their cardinalities
- Put everything together in a single E-R model
Next we will learn how to convert this E-R model to a physical database design. For this, proceed to lesson 6.
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