Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A company uses Azure SQL Database for an e-commerce application. The Orders table contains columns: OrderID (int, primary key), CustomerID (int), OrderDate (datetime), TotalAmount (decimal). Queries frequently filter by CustomerID and OrderDate to retrieve orders for a specific customer within a date range. Queries also need to retrieve a single order by OrderID quickly. Which indexing strategy will most improve the performance of these queries?
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) Keep the clustered index on OrderID and create a non-clustered index on (CustomerID, OrderDate)
The clustered index on OrderID ensures fast point lookups. The non-clustered index on (CustomerID, OrderDate) covers the range query, allowing SQL Server to perform an index seek without accessing the full table.
B
Distractor review
B) Change the clustered index to (CustomerID, OrderDate) and create a non-clustered index on OrderID
Changing the clustered index to (CustomerID, OrderDate) would improve the range query but degrade point lookups by OrderID because the clustered index would not be on OrderID, requiring a non-clustered index seek plus a key lookup.
C
Distractor review
C) Keep the clustered index on OrderID and create a non-clustered index on (OrderDate, CustomerID)
While this may help, the column order (OrderDate first) is less optimal for the typical query pattern which filters on CustomerID first, then OrderDate. The index would need to scan multiple date ranges for each customer, reducing efficiency.
D
Distractor review
D) Keep the clustered index on OrderID and create two separate non-clustered indexes on CustomerID and OrderDate
Separate indexes can help but the database may need to intersect them or perform a key lookup for each matched row, which is less efficient than a single covering composite index on (CustomerID, OrderDate).
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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Question 2
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Question 4
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Question 5
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Question 6
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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) Keep the clustered index on OrderID and create a non-clustered index on (CustomerID, OrderDate) — For fast point lookups on OrderID, a clustered index on OrderID is best because the clustered index determines the physical order. To efficiently support range queries on (CustomerID, OrderDate), a non-clustered index on those columns in that order provides a covering index for the common filter. Option A achieves both: clustered on OrderID, non-clustered covering on (CustomerID, OrderDate).
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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