Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A company uses Azure SQL Database for an HR system. The Employees table has a clustered index on EmployeeID. Queries frequently filter on DepartmentID and LastName and also retrieve the Salary column. The table contains over a million rows. Which index strategy will most improve query performance for these filters?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
A: Create a nonclustered index on (DepartmentID, LastName) INCLUDE (Salary)
This composite covering index includes all columns needed for the query, avoiding expensive key lookups into the clustered index.
B
Distractor review
B: Create a nonclustered index on LastName only
An index on LastName alone does not cover the DepartmentID filter, so the database would still need to scan or lookup rows, which is less efficient.
C
Distractor review
C: Create a nonclustered index on DepartmentID and another nonclustered index on LastName
Separate indexes could lead to index intersection, but this is less efficient than a single composite index and still may require key lookups for Salary.
D
Distractor review
D: Change the clustered index to (DepartmentID, LastName)
Changing the clustered index would alter the physical order of the table and could negatively affect other queries that rely on EmployeeID ordering, and it does not cover Salary.
Common exam trap
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Technical deep dive
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Related practice questions
Related DP-900 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
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FAQ
Questions learners often ask
What does this DP-900 question test?
Read the scenario before looking for a memorised answer.
What is the correct answer to this question?
The correct answer is: A: Create a nonclustered index on (DepartmentID, LastName) INCLUDE (Salary) — A composite nonclustered index on (DepartmentID, LastName) that includes Salary as a covering column allows queries to retrieve all needed data from the index without touching the clustered index (key lookup). This reduces I/O and improves query performance. Option B (index only on LastName) would still require filtering on DepartmentID, leading to partial scans. Option C (separate indexes) might use one index but would need key lookups for the other column. Option D (changing clustered index) would disrupt the primary key and could impact other queries. Therefore, option A is the most efficient.
What should I do if I get this DP-900 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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