Consider the given ER diagram for part of a BANK database (attached for reference). Each bank can have multiple branches, and each branch can have multiple accounts and loans.
(a) List the strong (nonweak) entity types in the ER diagram.
(b) Is there a weak entity type? If so, give its name, its partial key, and its identifying relationship.
(c) What constraints do the partial key and the identifying relationship of the weak entity type specify in this diagram?
(d) List the names of all relationship types, and specify the (min,max) constraint on each participation of an entity type in a relationship type. Justify your choices.
Guide On Rating System
Vote
(a) The strong (nonweak) entity types in the ER diagram are:
- Bank
- Branch
- Account
- Loan
(b) Yes, there is a weak entity type named "Transaction". Its partial key is "TransactionID" and its identifying relationship is with the entity type "Account".
(c) The partial key "TransactionID" and the identifying relationship with "Account" specify that each transaction is uniquely identified within an account. This means that a transaction cannot exist without an associated account.
(d) The names of all relationship types are:
- Bank has Branch (1,N) - This specifies that a bank can have multiple branches, but a branch can only belong to one bank. The (1,N) constraint indicates that a bank must have at least one branch, but a branch can exist without belonging to any bank.
- Branch has Account (1,N) - This specifies that a branch can have multiple accounts, but an account can only belong to one branch. The (1,N) constraint indicates that a branch must have at least one account, but an account can exist without belonging to any branch.
- Branch has Loan (1,N) - This specifies that a branch can have multiple loans, but a loan can only belong to one branch. The (1,N) constraint indicates that a branch must have at least one loan, but a loan can exist without belonging to any branch.
- Account has Transaction (0,N) - This specifies that an account can have multiple transactions, but a transaction can only belong to one account. The (0,N) constraint indicates that an account can have zero or more transactions, but a transaction can exist without belonging to any account.
- Account has Loan (0,1) - This specifies that an account can have at most one loan, but a loan can only belong to one account. The (0,1) constraint indicates that an account can have zero or one loan, and a loan can exist without belonging to any account.
Got a question with my answer?
Cheapmath.com is completely free!
Asking question is free.
Getting answers is free.
+99