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ER Assistant

Exercise

1. Select new from the file menu.2. Select entities from the insert menu on Figure 1.

Figure 1: Select Entities from Insert menu

3. An entity window on Figure 2 will open. Click on New button to create the newentity.

Figure 2: New Entity

4. Type DBST651_Students in the Name text box on Figure 3.

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Figure 3: Enter entity name

5. Click attributes button to open the Attribute window on Figure 4. Click new.

Figure 4: Attribute Window

6. Follow Figure 5to create StudentID attribute. type StudentID in the name text box

check the primary key check box select numeric for the datatype.

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Figure 5: StudentID attribute

7. Click on new again, and create an attribute FirstName on Figure 6. enter FirstName in the name text box set the datatype to varchar, and length to 10. make sure that the primary key text box is unchecked.

Figure 6: FirstName Attribute

8. Follow the same steps to create a LastName varchar attribute, and set thelength to 20.

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9. Create birthday attribute, and set the data type to date. Create grade attributeof type char length with length=1.

10.Figure 7 shows the list of 5 attributes you just added.

Figure 7: Students Entity with 5 Attributes11.Click close in the attribute window, and click new in the entity window.12.Create an entity named instructor with the following attributes:

InstructorID Numeric primary key

FirstName varchar with length=10

LastName varchar with length=20

YersExperience numeric

13.Create an entity named tutoring with the following attributes:RecordID Numeric primary key

SessionDate date

14.Click close in the entity window. Figure 8 shows the entities we just created.

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Figure 8: A diagram with 3 Entity but no relationships

15.Select relationships option from the insert menu on Figure 9

Figure 9: Select Relationships from Insert menu

16.Assume thata. Each instructor could have tutored zero or more students.b. Only one instructor is present in a session, and it is possible to have an

instructor who has not tutored any students.

Click new and follow Figure 10 to create the relationship betweenInstructor and Tutoring.

In the name text box, type Teaches. Entity one is an instructor. Check mandatory and one. (A tutoring session has to have an

instructor, but cannot have more than one instructor.)

Entity 2 is tutoring.

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Check optional and many check boxes.

Figure 10: Relationship between Instructor and Tutoring

17.Follow Figure 11 to create a relationship takes between dbst651_students andtutoring.

a. Each student may take zero or more tutoring sessions with differentinstructors.

b. Each session is only for one student.

Figure 11: Relationship between DBST651_Students and Tutoring

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18.Click close. Figure 12 shows the diagram with 3 entities and 2 relationships.

Figure 12: Final Diagram

19.You can use your mouse to move the entities and relationships to make yourdiagram look nice.

20.Choose Save from the file menu to save the diagram.