Question

Define Primary Key?

Hint:

Primary keys are essential for maintaining data integrity and establishing relationships between different tables in a relational database.

Answer 1

Primary Key:  

A Primary Key is a field (or column) in a database table that uniquely identifies each record (row) in that table. It must contain unique values and cannot contain NULL values. 

Key Characteristics:

• Uniqueness: Each primary key value must be unique across all records in the table.
• Non-null: A primary key cannot contain empty or NULL values.
• Unchanging: Primary key values should rarely, if ever, change.
• Single per table: Each table can have only one primary key.

Example: 

In a Students table, Student_ID can serve as the primary key because each student has a unique ID. 

 

Student_ID (Primary Key)	Name	Age	Grade
101	Alice	15	10
102	Bob	16	11
103	Charlie	15	10

Final Answer: 

\[ \boxed{\text{A primary key is a unique identifier for each record in a database table.}} \]