Course: Database Systems Discussion 1 (Chapter 3 - Course Textbook): Consider the ER diagram shown in Figure 3.22 for part of a BANK database (also below for reference). Each bank can have multiple

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Post 1:

Michael

Week 2 Discussion

COLLAPSE

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The strong entity types in the ER diagram are the BANK, ACCOUNT, LOAN, and CUSTOMER entities.

The weak entity is the BANK_BRANCH. Its identifying relationship is the BRANCHES relationship, and the partial key is the branch_no.

Since the branch_no is a partial key with an identifying relationship to BANK, it means that the branch_no may exist for multiple banks. To accurately identify which BANK_BRANCH, the branch_no, and code from BANK are required.

There are four relationship types: ACCTS, LOANS, A_C, L_C, and BRANCHES.

These are the relationships:

            A_C: M:N many-to-many

            L_C: M:N many-to-many

            ACCTS: 1:N one-to-many

            LOANS: 1:N one-to-many

            BRANCHES: 1:N one-to-many

A bank can have multiple branches (1:N), and each branch can have multiple accounts and loans (1:N). Each account and loan can have many customers (M:N).Bottom of Form

Post 2:

1 day ago

Jerome

Discussion 1

COLLAPSE

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Consider the ER diagram shown in Figure 3.22 for part of a BANK database (also below 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.

• The strong entity types: BANK, ACCOUNT, LOAN, and CUSTOMER

B) Is there a weak entity type? If so, give its name, its partial key, and its identifying relationship.

• The weak entity type: BANK_BRANCH

• Partial key: Branch_no

• Identifying relationship: BRANCHES

C) What constraints do the partial key and the identifying relationship of the weak entity type specify in this diagram?

• Each branch has a unique branch number

• Each BANK_BRANCH will have exactly 1 BANK

• Each BANK will have 1 or more BANK_BRANCH

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.

• BRANCHES consists of BANK (1,N) and BANK_BRANCH (1,1)

  • BANK and BANK_BRANCH have total participation

  • Each bank must have one or more branches, and each branch must have exactly one bank

• ACCTS consists of BANK_BRANCH (0,N) and ACCOUNT (1,1)

  • BANK_BRANCH has partial participation and ACCOUNT has total participation

  • Each branch can have zero or more accounts, and each account must have exactly one branch

• A_C consists of ACCOUNT (1,N) and CUSTOMER (0,N)

  • ACCOUNT has total participation and CUSTOMER has partial participation

  • Each account must have one or more customers, and each customer can have zero or more accounts

• LOANS consists of BANK_BRANCH (0,N) and LOAN (1,1)

  • BANK_BRANCH has partial participation and LOAN has total participation

  • Each branch can have zero or more loans, and each loan must have exactly one branch

• L_C consists of LOAN (1,N) and CUSTOMER (0,N)

  • LOAN has total participation and CUSTOMER has partial participation

  • Each loan must have one or more customers, and each customer can have zero or more loans

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