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Primary Key, Foreign Key, and Constraints – Ensuring data integrity.

MCQ Question 1 of 10

Question 1: Primary Key - Uniqueness in RDBMS

What is the main purpose of a Primary Key in a relational table?

To allow duplicate valuesTo uniquely identify each rowTo create multiple indexesTo store relationships

Question 2: Foreign Key - Relationships in RDBMS

What does a Foreign Key in a table do?

Defines a unique record within a tableEstablishes a link to the primary key in another tableStores duplicate values onlyActs as a backup key

Question 3: NOT NULL Constraint - Column Rules in RDBMS

Which constraint ensures that a column must always have a value?

UNIQUENOT NULLDEFAULTCHECK

Question 4: UNIQUE Constraint - Data Integrity in RDBMS

What is the purpose of the UNIQUE constraint?

Allows multiple duplicate valuesEnsures all values in a column are differentDefines a default valueActs as a foreign key

Question 5: CHECK Constraint - Validation in RDBMS

Which constraint can be used to validate values before inserting into a column?

PRIMARY KEYCHECKFOREIGN KEYUNIQUE

Question 6: DEFAULT Constraint - Automatic Values in RDBMS

What does the DEFAULT constraint do?

Assigns a default value when no value is providedEnsures uniqueness of rowsDefines relationshipsPrevents null values

Question 7: Composite Primary Key - Multiple Columns in RDBMS

What is a composite primary key?

A primary key made up of a single columnA primary key that includes two or more columnsA foreign key combined with a unique keyA backup key for integrity

Question 8: Referential Integrity - Foreign Key Role in RDBMS

What happens if a foreign key value does not match a primary key in the referenced table?

The row is still insertedReferential integrity is violated, insertion failsA default value is assignedData is ignored

Question 9: Primary Key vs Unique Constraint - RDBMS

Which of the following is true about Primary Key vs Unique?

Both allow multiple NULL valuesPrimary Key allows one NULL, Unique does notPrimary Key does not allow NULL, Unique allows one NULLBoth do not allow NULL values

Question 10: Importance of Constraints - Data Integrity in RDBMS

Why are constraints like Primary Key, Foreign Key, and NOT NULL important?

To increase redundancyTo enforce data integrity and consistencyTo speed up queries onlyTo allow duplicate and null values freely