What does the entity integrity rule state
Correct answer: B. Each entity must have a primary key
- A. No primary key attribute can be null
- B. Each entity must have a primary key
- C. Primary key must have only one attribute
Explanation
The entity integrity rule ensures that every table in a relational database has a primary key, and that the primary key cannot contain null values. This is important because the primary key is used to uniquely identify each row in the table. If a primary key could be null, then there would be no way to guarantee that each row was unique. In simpler terms, the entity integrity rule makes sure that every record in a database table has a unique identifier that can't be blank. This helps to ensure that the data in the database is accurate and consistent.
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