SQL Keys MCQ Primary Key Foreign Key Practice Questions

Direction: Choose the correct option

What is a primary key?

A. Index for searching

B. Key to another table

C. First column in table

D. Unique identifier for each row

Direction: Choose the correct option

CREATE TABLE students (
    id INT PRIMARY KEY,
    name VARCHAR(50)
);

What constraint does id have?

A. Foreign key

B. Primary key

C. Unique only

D. Not null

Direction: Choose the correct option

What is a foreign key?

A. Key that references another table

B. Key that is indexed

C. Key that is first in table

D. Key that is unique

Direction: Choose the correct option

How many primary keys can a table have?

A. One

B. Zero

C. Unlimited

D. Multiple

Direction: Choose the correct option

What's the difference between PRIMARY KEY and UNIQUE?

A. Primary key cannot be NULL, UNIQUE can

B. Primary key allows NULL

C. Unique is faster

D. Both are same

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