Which of the following is a valid SQL constraint that ensures a column's values are all distinct? MCQ with Answer and Explanation

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Which of the following is a valid SQL constraint that ensures a column's values are all distinct?

A. Both A and B

B. UNIQUE

C. DISTINCT

D. PRIMARY KEY

Answer: Option A

Solution (By JKExamLibrary)

Both UNIQUE and PRIMARY KEY enforce uniqueness. PRIMARY KEY also implies NOT NULL.

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

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Practice More Database Management System (DBMS) Questions

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What is a data mart?

A. A type of database

B. A backup technique

C. A query language

D. A subset of a data warehouse focused on a specific business unit or function

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Correct Answer: Option D

Explanation:
A data mart is a specialized data warehouse for a specific department, team, or subject area.

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

Question #2

Which of the following is a DML statement?

A. CREATE

B. ALTER

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Correct Answer: Option C

Explanation:
UPDATE is a Data Manipulation Language (DML) command used to modify existing records in a table. CREATE, ALTER, DROP are DDL.

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

Question #3

What value represents missing, unknown, or inapplicable data in a relational database?

A. Void

B. Blank Space (' ')

C. NULL

D. Zero (0)

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Correct Answer: Option C

Explanation:
NULL is a special marker used in SQL to indicate the absence of a value or that the data is missing, unknown, or not applicable.

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

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