Q4. What do you understand by a primary key?
Ans. In a database, a primary key is used to uniquely identify the data in a field. If we assign a primary key to a column of a table, it means that each field in that column contains a unique value.
Q5. Can a primary key contain null value?
Ans. No, primary key cannot contain null value.
Q3. What Do you understand by a primary key?
Ans. The key that helps us to uniquely identify a record n a table.
Q7. What is the significance of a primary key?
Ans. A primary key is used to uniquely identify which record in a table. In other words, a column with a primary key will not contain duplicate information in any of its records. For example, in the Employee_Details table, we can set the primary key in the Emp_Code column, which contains the employee code. In this case, duplicate values are not possible in the column.
Q153. Define Primary Key.
Ans. Primary Key is set of one or more attributes that can uniquely identify tuples within a relation.