Entity integrity rules in RDBMS

For entity integrity rules, each table has a primary key.

Primary keys cannot have NULL values.

Student_ID . We cannot treat Student_Awards as a primary key because not every student will receive that award.

Let’s see another example -

In the above table, the primary key is

• Each table has a primary key, such as
Student_ID
• of the Student table. Each entity is unique.
• The relational primary key of each row must have a unique value.
• Primary keys cannot have NULL values ​​and must be unique.
• An example could be Employee_ID
• in the Employee table cannot be empty.

The above is the detailed content of Entity integrity rules in RDBMS. For more information, please follow other related articles on the PHP Chinese website!