Which aggregate function is used to count the number of rows in a table? MCQ with Answer and Explanation

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Which aggregate function is used to count the number of rows in a table?

A. AVG

B. SUM

C. COUNT

D. MAX

Answer: Option C

Solution (By JKSSB Mock Tests)

COUNT returns the number of rows in a table or group.

This question belongs to: Computer Database Management System (DBMS)

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Practice More Database Management System (DBMS) Questions

Question #1

Which of the following is a type of lock in a database?

A. None

B. Shared lock

C. Exclusive lock

D. Both A and B

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Correct Answer: Option D

Explanation:
Shared locks allow multiple transactions to read a resource, while exclusive locks allow only one transaction to write.

This question belongs to: Computer Database Management System (DBMS)

Question #2

Which constraint ensures that a column cannot accept or store an unassigned or missing value?

A. NOT NULL

B. UNIQUE

C. DEFAULT

D. CHECK

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Correct Answer: Option A

Explanation:
The NOT NULL constraint explicitly forces a column to always contain a value, preventing blank or NULL entries.

This question belongs to: Computer Database Management System (DBMS)

Question #3

A key that consists of more than one attribute to uniquely identify rows in a table is called a what?

A. Primary Key

B. Composite Key

C. Secondary Key

D. Foreign Key

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Correct Answer: Option B

Explanation:
When a primary key or unique key comprises two or more columns (attributes) combined together, it is known as a Composite Key.

This question belongs to: Computer Database Management System (DBMS)

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