What is the purpose of the SQL 'NULL' value? MCQ with Answer and Explanation

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What is the purpose of the SQL 'NULL' value?

A. To represent zero

B. To represent an error

C. To represent empty string

D. To represent missing or unknown data

Answer: Option D

Solution (By JKSSB Mock Tests)

NULL is a special marker indicating that a value is unknown or missing, not the same as zero or empty string.

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

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Which SQL function returns the current date and time?

A. GETDATE()

B. CURDATE()

C. NOW()

D. All of the above depending on the DBMS

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Correct Answer: Option D

Explanation:
Different DBMSs have different functions: MySQL NOW(), SQL Server GETDATE(), etc. But all return current date/time.

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

Question #2

The JOIN operation in SQL is used to:

A. Delete rows

B. Sort data

C. Combine rows from two or more tables

D. Create a new database

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Correct Answer: Option C

Explanation:
JOIN combines data from multiple tables based on related columns.

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

Question #3

In SQL, which statement is used to change a user's password?

A. ALTER USER

B. MODIFY USER

C. UPDATE USER

D. CHANGE USER

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Correct Answer: Option A

Explanation:
ALTER USER is used in many DBMS to change user attributes, including password. The exact syntax varies by DBMS.

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

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