Test by Bikram | Mock GATE | Test 3 | Question: 2

Question

Which of the following statements are TRUE?

1.    An SQL query automatically eliminates duplicates.
2.    An SQL query will not work if there are no indexes on the relations.
3.    SQL permits attribute names not to be repeated in the same relation.

• A. I and III  
• B. II only
• C. III only
• D. I and II only

Answer 1

1. False , SQL wont remove duplicates like relational algebra projection, we have to remove it explicilty by distinct.

2. False , If there are no indexes on the relation SQL will either chose one/more on its own or simply work without any index. No index would just slow the query but it will surely work.

3. True , SQL does not permit 2 attributes to have same name in a relation.

Hence option C is correct.