JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD MCA II DATABASE MANAGEMENT SYSTEMS Previous Question Paper (October/ November - 2020 - R13)

A strong entity set is an entity set that contains sufficient attributes to form a primary key. Every entity in a strong entity set is uniquely identified by its own attributes. In an ER diagram, it is represented by a rectangular box.

A weak entity set is an entity set that does not have sufficient attributes to form a primary key. The existence of a weak entity depends on the existence of a identifying entity set (or owner entity set). The primary key of a weak entity is formed by the primary key of the identifying entity set plus the discriminator (or partial key) of the weak entity. In an ER diagram, a weak entity set is represented by a double-lined rectangular box, and its relationship to the identifying entity is represented by a double-lined diamond.

In a banking enterprise ER diagram, the core entities typically include Customer, Account, Branch, and Loan.

• Customer: Attributes include Customer-ID (primary key), Customer-Name, and Customer-Street.
• Account: Attributes include Account-Number (primary key) and Balance.
• Branch: Attributes include Branch-Name (primary key), Branch-City, and Assets.
• Relationships: A 'Depositor' relationship links Customer to Account (many-to-many). A 'Borrower' relationship links Customer to Loan (many-to-many). An 'Account-Branch' relationship links Account to Branch (many-to-one), and a 'Loan-Branch' relationship links Loan to Branch (many-to-one).

The diagram illustrates how customers hold accounts or loans at specific branches, maintaining referential integrity across the banking system.