Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A company uses Azure SQL Database for an e-commerce platform. The 'Orders' table has millions of rows with columns OrderID (primary key), CustomerID, OrderDate, and TotalAmount. Queries often filter by CustomerID (equality) and OrderDate (range). Currently, these queries are slow. Which index should be created to improve 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
Distractor review
A nonclustered index on OrderID
An index on OrderID does not help queries filtering by CustomerID and OrderDate. The primary key already has a clustered index on OrderID, which is used for lookups by OrderID.
B
Best answer
A nonclustered index on (CustomerID, OrderDate)
This composite index covers the query predicate perfectly. CustomerID is the equality column, and OrderDate is the range column. The index allows the database engine to efficiently locate rows for a specific customer and then scan a small range of dates.
C
Distractor review
A nonclustered index on OrderDate
Indexing only OrderDate would not help the CustomerID filter. The database would still need to scan all rows for the requested customer after filtering by date.
D
Distractor review
A clustered index on CustomerID
The table already has a clustered index on OrderID (the primary key). You cannot have more than one clustered index on a table. Rebuilding the clustered index on CustomerID would change the physical order of rows and may affect other queries.
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 nonclustered index on (CustomerID, OrderDate) — The correct answer is to create a composite nonclustered index on (CustomerID, OrderDate). This index directly supports the query predicate: CustomerID equality followed by OrderDate range. A nonclustered index on CustomerID alone would help only the equality filter, but the range filter would still require a full scan of the rows for that customer. A composite index with the equality column first, then the range column, allows efficient seek operations. Creating a clustered index on CustomerID is not possible because the table already has a clustered index on OrderID (primary key). Indexing only OrderDate would not help the CustomerID filter. Note: Azure SQL Database supports nonclustered indexes that can be created without affecting the existing clustered index.
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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