Entity Integrity Rule in RDBMS

RDBMSDatabaseMySQL

For Entity Integrity Rule, each table has a Primary Key.

Primary Key cannot have NULL value.

<Student>

Student_ID
Student_Awards
Student_Awards


Above, you can see our primary key is Student_ID. We cannot consider Student_Awards as the primary key since not every student would have received the award.

Let us see another example −

<Employee>

Employee_ID
Employee_Name
Employee_Age
Employee_Location


In the above table, the Primary Key is Employee_ID

Let us now summarize the Entity Integrity Rule −

  • Make sure that each tuple in a table is unique.
  • Every table mush has a primary key, for example, Student_ID for a Student table.
  • Every entity is unique.
  • The relations Primary Key must have unique values for each row.
  • Primary Key cannot have NULL value and must be unique.
  • Example can be an Employee_ID cannot be null in an Employee table.
raja
Published on 04-Jul-2018 00:48:58
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