In SQL, what does the 'IS NULL' operator check? MCQ with Answer and Explanation

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In SQL, what does the 'IS NULL' operator check?

A. Whether a value is missing (null)

B. Whether a value is zero

C. Whether a value is empty string

D. Whether a value equals NULL

Answer: Option A

Solution (By JKSSB Mock Tests)

IS NULL is used to test for NULL values, because NULL is not equal to anything.

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

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Question #1

What is the purpose of the SQL 'GROUP BY' clause?

A. To join tables

B. To sort the result set

C. To filter rows

D. To group rows that have the same values in specified columns into summary rows

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Correct Answer: Option D

Explanation:
GROUP BY organizes data into groups based on the values of one or more columns, often used with aggregate functions.

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

Question #2

Which of the following is a valid SQL statement to create a table?

A. Both A and B

B. CREATE TABLE table_name (column1 datatype, column2 datatype);

C. CREATE TABLE table_name AS SELECT ...;

D. Neither

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Correct Answer: Option A

Explanation:
Both syntaxes are valid: direct CREATE TABLE with columns, and CREATE TABLE ... AS SELECT to create a table from a query result.

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

Question #3

A candidate key is:

A. Always the primary key

B. A minimal super key

C. A foreign key only

D. Any key with duplicates

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Correct Answer: Option B

Explanation:
A candidate key is a minimal set of attributes that can uniquely identify a tuple.

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

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