Specifies enterprise schema that represents the overall logical structure of a database graphically.
Consists of Entities, Attributes, and Relationships among Entities
Entities
A Unit object , can be of two types:
- Strong: Independent (has primary key)
- Weak: Dependent on other Entity - double rectangle
Example:
Attributes
Properties that define the entity type
Represented as:
Key (ex: Roll_No) - underlined Composite (ex: Address) - has Derived (ex: Age) - dotted Multivalued (Phone_No)