database unit 4

Conceptual Model

When designing a database, we usually start with a

Strong Entities

Entities that exist independently and have their own primary key

Weak Entities

Entities that cannot exist without being related to a strong entity. They depend on a strong entity for their identification.

Simple Attributes

directly mapped as columns.

Composite Attributes

break into atomic attributes.

Multivalued Attributes

create a separate table.

True

In a relational database, relationships connect entities to reflect how data is linked in the real world. ERDs show these relationships clearly, but they must be translated into relational tables to be implemented in SQL.

True

When we map an ERD into a relational schema, we don’t just create tables for entities and relationships. We also need to specify constraints and keys to ensure that the data in the database.