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

Question
Which of the following is a valid SQL constraint that ensures a column's values are all distinct?
A. Both A and B
B. DISTINCT
C. UNIQUE
D. PRIMARY KEY
Answer: Option A
Solution (By JKSSB Mock Tests)
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

Question #1
Which operator is used in SQL to compare a value to a set of values returned by a subquery?
A. IN
B. EXISTS
C. BETWEEN
D. LIKE
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Correct Answer: Option A

Explanation:
IN checks if a value matches any value in a list or subquery result set.
This question belongs to: Computer Database Management System (DBMS)
Question #2
What is the purpose of the SQL 'WITH' clause (Common Table Expression)?
A. To delete data
B. To define a temporary result set that can be referenced within a query
C. To update data
D. To create a view
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Correct Answer: Option B

Explanation:
A Common Table Expression (CTE) provides a temporary named result set that can be used within a SELECT, INSERT, UPDATE, or DELETE statement.
This question belongs to: Computer Database Management System (DBMS)
Question #3
Which condition-tester returns TRUE if a subquery returns one or more records, and FALSE if the subquery returns no rows?
A. IN
B. EXISTS
C. ALL
D. ANY
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Correct Answer: Option B

Explanation:
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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