Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A company has a table named 'Sales' in Azure SQL Database with columns: SaleID (int, primary key), ProductID (int), SaleDate (datetime), Quantity (int), UnitPrice (decimal), TotalAmount (computed column). Queries frequently run to retrieve the total Quantity and UnitPrice for a specific ProductID over a date range. The query filters on ProductID and SaleDate and selects only Quantity and UnitPrice. Which index would most improve query performance?
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
Nonclustered index on (ProductID, SaleDate) INCLUDE (Quantity, UnitPrice)
This covering index includes all columns needed by the query (Quantity, UnitPrice) as included columns, and the key columns (ProductID, SaleDate) support efficient filtering. The query can be satisfied entirely from the index without key lookups.
B
Distractor review
Nonclustered index on (SaleDate) INCLUDE (Quantity, UnitPrice)
This index has SaleDate as the key, but the query also filters on ProductID. Without ProductID as a key column, the database may need to scan many rows for each date range, leading to poor performance.
C
Distractor review
Clustered index on (ProductID, SaleDate)
A clustered index defines the physical order and includes all columns, but changing the clustered index order would require reordering the entire table, which may cause fragmentation and impact other queries. Additionally, a covering nonclustered index is often lighter for this specific query.
D
Distractor review
Nonclustered index on (ProductID) INCLUDE (Quantity, UnitPrice)
This index includes ProductID as the key, but the query also filters on SaleDate. Without SaleDate in the key, the database would need to scan all rows for the given ProductID and then apply a residual predicate on SaleDate, which is less efficient.
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: Nonclustered index on (ProductID, SaleDate) INCLUDE (Quantity, UnitPrice) — A nonclustered index on ProductID and SaleDate that includes Quantity and UnitPrice is a covering index for the query. It allows the query to retrieve all required columns directly from the index without needing to access the clustered index (key lookup). This minimizes I/O and improves performance. The other options are less efficient because they either do not cover the query or cause unnecessary key lookups.
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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