- A
Create a nonclustered index on (CustomerID, OrderDate DESC) with included column TotalAmount
This index directly supports the filter on CustomerID and the range/order on OrderDate, and includes TotalAmount to avoid key lookups, making it the most efficient.
- B
Create a nonclustered index on (OrderDate DESC, CustomerID) with included column TotalAmount
Why wrong: This index orders by date first, so for a specific CustomerID, the database would need to scan a potentially large range of dates before applying the CustomerID filter, which is less efficient.
- C
Change the clustered index to be on (CustomerID, OrderDate DESC)
Why wrong: Changing the clustered index from the primary key OrderID could disrupt other queries and operations; also, a clustered index on these columns might cause page splits and fragmentation due to sequential inserts by OrderID.
- D
Create a nonclustered index on (OrderDate DESC) without including TotalAmount
Why wrong: This index does not filter by CustomerID, so the query would need to scan many rows or perform a key lookup for each row, resulting in poor performance.
DP-900 Practice Question: Identify considerations for relational data on Azure
This DP-900 practice question tests your understanding of identify considerations for relational data on azure. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. A key principle to apply: nonclustered indexes improve query performance by providing fast data access paths.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company uses Azure SQL Database for an e-commerce platform. The Orders table has columns: OrderID (primary key, clustered), CustomerID, OrderDate, TotalAmount. Queries frequently filter on CustomerID and a range of OrderDate, and then sort the results by OrderDate in descending order. The queries also return the TotalAmount column. Which indexing strategy will most improve query performance for these operations?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"primary"Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Create a nonclustered index on (CustomerID, OrderDate DESC) with included column TotalAmount
Option A is correct because it creates a covering index that matches the query's filter predicates (CustomerID equality, OrderDate range) and sort order (OrderDate DESC). By including TotalAmount as an included column, the index fully satisfies the query without needing to access the clustered index (key lookup), minimizing I/O and improving performance.
Key principle: Nonclustered indexes improve query performance by providing fast data access paths.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Create a nonclustered index on (CustomerID, OrderDate DESC) with included column TotalAmount
Why this is correct
This index directly supports the filter on CustomerID and the range/order on OrderDate, and includes TotalAmount to avoid key lookups, making it the most efficient.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Nonclustered indexes improve query performance by providing fast data access paths.
- ✗
Create a nonclustered index on (OrderDate DESC, CustomerID) with included column TotalAmount
Why it's wrong here
This index orders by date first, so for a specific CustomerID, the database would need to scan a potentially large range of dates before applying the CustomerID filter, which is less efficient.
- ✗
Change the clustered index to be on (CustomerID, OrderDate DESC)
Why it's wrong here
Changing the clustered index from the primary key OrderID could disrupt other queries and operations; also, a clustered index on these columns might cause page splits and fragmentation due to sequential inserts by OrderID.
- ✗
Create a nonclustered index on (OrderDate DESC) without including TotalAmount
Why it's wrong here
This index does not filter by CustomerID, so the query would need to scan many rows or perform a key lookup for each row, resulting in poor performance.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose an index with the sort column first (Option B) or forget to include the non-key column (Option D), not realizing that covering indexes with the correct key order eliminate expensive key lookups and sorts.
Detailed technical explanation
How to think about this question
In Azure SQL Database, nonclustered indexes with included columns allow the query to be fully covered without touching the clustered index, reducing logical reads. The key order matters: leading with the equality column (CustomerID) enables efficient seek operations, while the range column (OrderDate) is used for range scans and sorting. The DESC keyword on OrderDate aligns with the query's ORDER BY DESC, avoiding a sort operation in the query plan.
KKey Concepts to Remember
- Nonclustered indexes improve query performance by providing fast data access paths.
- Column order in a nonclustered index is crucial for efficient filtering and sorting.
- Included columns in a nonclustered index avoid key lookups to the base table.
- A covering index contains all columns needed by a query, preventing additional data retrieval.
TExam Day Tips
- 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.
Key takeaway
Nonclustered indexes improve query performance by providing fast data access paths.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
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Review nonclustered indexes improve query performance by providing fast data access paths., then practise related DP-900 questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this DP-900 question test?
Identify considerations for relational data on Azure — This question tests Identify considerations for relational data on Azure — Nonclustered indexes improve query performance by providing fast data access paths..
What is the correct answer to this question?
The correct answer is: Create a nonclustered index on (CustomerID, OrderDate DESC) with included column TotalAmount — Option A is correct because it creates a covering index that matches the query's filter predicates (CustomerID equality, OrderDate range) and sort order (OrderDate DESC). By including TotalAmount as an included column, the index fully satisfies the query without needing to access the clustered index (key lookup), minimizing I/O and improving performance.
What should I do if I get this DP-900 question wrong?
Review nonclustered indexes improve query performance by providing fast data access paths., then practise related DP-900 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
What is the key concept behind this question?
Nonclustered indexes improve query performance by providing fast data access paths.
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Last reviewed: Jun 11, 2026
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