What is a composite key in a database? MCQ with Answer and Explanation

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What is a composite key in a database?

A. A key that references another table

B. A key that is always a foreign key

C. A key that is made up of multiple columns

D. A key that is a single column

Answer: Option C

Solution (By JKSSB Mock Tests)

A composite key is a primary key that consists of two or more columns to uniquely identify a row.

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

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Question #1

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Which wildcard character is used with the SQL LIKE operator to represent zero, one, or multiple characters?

A. Hash (#)

B. Percentage sign (%)

C. Underscore (_)

D. Ampersand (&)

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Correct Answer: Option B

Explanation:
The percentage sign (%) is used as a wildcard character to match any sequence of zero or more characters in an SQL LIKE string comparison query.

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

Question #2

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What is the purpose of the SQL 'DEFAULT' constraint?

A. To set a foreign key

B. To provide a default value for a column when no value is supplied

C. To define a primary key

D. To enforce uniqueness

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Correct Answer: Option B

Explanation:
DEFAULT assigns a default value to a column if an INSERT statement does not specify a value.

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

Question #3

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Which of the following ensures data integrity in RDBMS?

A. User input without checks

B. Constraints like primary key, foreign key

C. Random data entry

D. No validation rules

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Correct Answer: Option B

Explanation:
Integrity constraints such as keys enforce rules for valid data.

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

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