This is the DBMS questions and answers section on "Indexes" with explanation for various interview, competitive examination and entrance test. Solved examples with detailed answer description, explanation are given and it would be easy to understand.
1. What is the purpose of index in sql server
- A. To enhance the query performance
- B. To provide an index to a record
- C. To perform fast searches
- D. All of the mentioned
Answer: Option D
Explanation:
All of the mentioned
A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes.
2. How many types of indexes are there in sql server?
Answer: Option B
Explanation:
2
They are clustered index and non clustered index.
3. How non clustered index point to the data?
- A. It never points to anything
- B. It points to a data row
- C. It is used for pointing data rows containing key values
- D. None of the mentioned
Answer: Option C
Explanation:
It is used for pointing data rows containing key values
Nonclustered indexes have a structure separate from the data rows. A nonclustered index contains the nonclustered index key values and each key value entry has a pointer to the data row that contains the key value.
4. Which one is true about clustered index?
- A. Clustered index is not associated with table
- B. Clustered index is built by default on unique key columns
- C. Clustered index is not built on unique key columns
- D. None of the mentioned
Answer: Option B
Explanation:
Clustered index is built by default on unique key columns
Nonclustered indexes have a structure separate from the data rows. A nonclustered index contains the nonclustered index key values and each key value entry has a pointer to the data row that contains the key value.
5. What is true about indexes?
- A. Indexes enhance the performance even if the table is updated frequently
- B. It makes harder for sql server engines to work to work on index which have large keys
- C. It doesn’t make harder for sql server engines to work to work on index which have large keys
- D. None of the mentioned
Answer: Option B
Explanation:
It makes harder for sql server engines to work to work on index which have large keys
Indexes tend to improve the performance.
