Question

Your boss shows you the ER model that he has spent a couple days to finish. You are asked to make some comments ont How will you use your skills from this course to modify and/or improve this ER model? (1) If you decide to modify the ER model, draw the new diagram and EXPLAIN in detail why you want to modify it. If you decide to keep the ER model unchanged, EXPLAIN why it is perfect and no need to be changed. ("I do not want to offend my boss." is the best but invalid reason.) (2) Convert it into relations Account、) Name number balance Accounts balance of

Answer 1

1)

The given ER diagram shows two entity. One is weak entity (balance) and the other is strong (Account) entity. The complete scenario is not given. As per the rules of the ER diagram the week entity also have a unique attribute though the primary key of the week entity can only the declared by combining the unique key of the weak entity and primary key (foreign key for week entity balance). This uniquely selects a row in tuple.

Below is the updated ERD -

AccountlD BalancelD Name Balance Account Paty Of Balance

2)

The relational schema of the modified ER is given below. It has two entities.

Balance Account AccountID Name BalancelD AccountID (FK)