Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A company has an Azure SQL Database with an 'Orders' table containing millions of rows. The table has a clustered index on OrderID (primary key). Queries frequently filter by CustomerID (equality) and OrderDate (range). These queries are slow and cause high logical reads. Which index strategy will most improve performance for these specific 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
Create a non-clustered index on (CustomerID, OrderDate).
This composite index matches the query pattern exactly: it allows index seek on CustomerID and then range scan on OrderDate, providing optimal performance.
B
Distractor review
Rebuild the clustered index on (OrderDate, CustomerID).
Changing the clustered index would rearrange the entire table, potentially harming other queries that rely on OrderID ordering. It is a major change with broader impact and may not be the best first approach.
C
Distractor review
Create a non-clustered index on OrderDate.
This index would require filtering on CustomerID separately, likely leading to many key lookups and still high reads. It is not as efficient as a composite covering index.
D
Distractor review
Create a filtered index on OrderDate for recent dates.
A filtered index would only benefit queries restricted to the filtered condition (e.g., recent dates) and would not help for historical range queries. It is too narrow in scope.
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: Create a non-clustered index on (CustomerID, OrderDate). — For queries that filter with equality on CustomerID and a range on OrderDate, a non-clustered composite index on (CustomerID, OrderDate) is ideal. The index first seeks exactly on CustomerID (equality), then scans a narrow range of OrderDate values. This minimizes reads and avoids key lookup overhead. Changing the clustered index would impact all other queries and involves more risk. A simple non-clustered index on OrderDate alone would not help with CustomerID filtering efficiently. A filtered index is too narrow and may not cover all queries.
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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