Database-Management-System
December 7, 2023Database-Management-System
December 7, 2023Database-Management-System
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Question 39
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Which of the following is/are correct?
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An SQL query automatically eliminates duplicates
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An SQL query will not work if there are no indexes on the relations
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SQL permits attribute names to be repeated in the same relation
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None of the above
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Question 39 Explanation:
→ SQL won’t remove duplicates like relational algebra projection, we have to remove it explicitly by distinct.
→ If there are no indexes on the relation SQL, then also it works.
→ SQL does not permit 2 attributes to have same name in a relation.
→ If there are no indexes on the relation SQL, then also it works.
→ SQL does not permit 2 attributes to have same name in a relation.
Correct Answer: D
Question 39 Explanation:
→ SQL won’t remove duplicates like relational algebra projection, we have to remove it explicitly by distinct.
→ If there are no indexes on the relation SQL, then also it works.
→ SQL does not permit 2 attributes to have same name in a relation.
→ If there are no indexes on the relation SQL, then also it works.
→ SQL does not permit 2 attributes to have same name in a relation.