Which condition-tester returns TRUE if a subquery returns one or more records, and FALSE if the subquery returns no rows? MCQ with Answer and Explanation

Question

Which condition-tester returns TRUE if a subquery returns one or more records, and FALSE if the subquery returns no rows?

A. ANY

B. ALL

C. IN

D. EXISTS

Answer: Option D

Solution (By JKSSB Mock Tests)

The EXISTS operator is used to test for the presence of any records in a subquery, returning TRUE as soon as a single matching row is encountered.

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

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Question #1

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Which of the following is a valid SQL statement to add a primary key to an existing table?

A. Both A and C

B. ALTER TABLE table_name ADD CONSTRAINT pk_name PRIMARY KEY (column_name);

C. ADD PRIMARY KEY ON table_name (column_name);

D. ALTER TABLE table_name ADD PRIMARY KEY (column_name);

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Correct Answer: Option A

Explanation:
Both syntaxes are valid: ADD PRIMARY KEY (column) and ADD CONSTRAINT ... PRIMARY KEY (column).

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

Question #2

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Which normal form addresses partial dependencies, i.e., non-prime attributes dependent on part of a composite primary key?

A. 2NF

B. 1NF

C. 3NF

D. BCNF

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Correct Answer: Option A

Explanation:
Second Normal Form (2NF) eliminates partial dependencies by ensuring all non-key attributes are fully functionally dependent on the entire primary key.

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

Question #3

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Which type of JOIN combines all rows from the left table and all rows from the right table, filling in NULLs wherever a match is missing on either side?

A. Full Outer Join

B. Inner Join

C. Natural Join

D. Cross Join

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Correct Answer: Option A

Explanation:
A Full Outer Join combines the behavior of both Left and Right Outer Joins, returning all rows from both tables and applying NULL values where matches do not exist.

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

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