SQL Indexes MCQ Questions
11. Indexes can also be unique?
A. Yes
B. No
C. Maybe
D. Can't say
View Answer
Ans : A
Explanation: Indexes can also be unique, like the UNIQUE constraint.
12. A ______ index does not allow any duplicate values to be inserted into the table.
A. Implicit
B. Unique
C. single-column
D. Composite
View Answer
Ans : B
Explanation: A unique index does not allow any duplicate values to be inserted into the table.
13. Which of the following is condition where indexes be avoided?
A. Indexes should not be used on small tables
B. Tables that have frequent, large batch updates or insert operations
C. Columns that are frequently manipulated should not be indexed.
D. All of the above
View Answer
Ans : D
Explanation: All the statement are condition where indexes be avoided.
14. What is the syntax for Single-Column Indexes?
A. CREATE INDEX index_name ON table_name (column_name);
B. CREATE SINGLE-COLUMN INDEX index_name ON table_name (column_name);
C. CREATE INDEX SINGLE-COLUMN index_name ON table_name (column_name);
D. ALTER SINGLE-COLUMN INDEX index_name ON table_name (column_name);
View Answer
Ans : A
Explanation: The basic syntax is as follows : CREATE INDEX index_name ON table_name (column_name);
15. Which of the following index are automatically created by the database server when an object is created?
A. Implicit
B. Unique
C. single-column
D. Composite
View Answer
Ans : A
Explanation: Implicit indexes are indexes that are automatically created by the database server when an object is created. Indexes are automatically created for primary key constraints and unique constraints.
16. A _________ query is a query where all the columns in the query’s result set are pulled from non-clustered indexes.
A. B-Tree
B. Non Clustered
C. Covered
D. Clustered
View Answer
Ans : C
Explanation: A covered query is a query where all the columns in the query’s result set are pulled from non-clustered indexes.
17. _______________ have a structure separate from the data rows?
A. B-Tree
B. Non Clustered
C. Covered
D. Clustered
View Answer
Ans : B
Explanation: 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.
18. Does index take space in the disk?
A. Yes
B. No
C. It stores memory as and when required
D. Indexes take no space
View Answer
Ans : A
Explanation: Indexes take memory slots which are located on the disk.
19. 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. All of the above
View Answer
Ans : C
Explanation: 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.
20. Indexes used to improve the performance.
A. YES
B. NO
C. Maybe
D. Can't say
View Answer
Ans : A
Explanation: Indexes tend to improve the performance.
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