- A
A. Create a nonclustered index on OrderDate only.
Why wrong: This index would help with ordering by OrderDate, but the query first needs to filter on CustomerID. Without an index on CustomerID, a full scan or inefficient lookup is needed.
- B
B. Create a filtered index on CustomerID where Status = 'Active'.
Why wrong: A filtered index is limited to rows that meet a specific condition. If queries filter by CustomerID regardless of Status, this index may be incomplete and not used.
- C
C. Create a nonclustered index on (CustomerID, OrderDate).
This composite index allows efficient seek on CustomerID and then an ordered scan of OrderDate, covering both the filter and the sort without additional operations.
- D
D. Create a nonclustered index on OrderID and OrderDate.
Why wrong: This index does not include CustomerID, so it cannot be used to filter on CustomerID efficiently. It would not help the query.
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: composite indexes improve queries filtering and sorting on multiple columns.. 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 application. The Orders table has millions of rows. Queries that filter on CustomerID and order by OrderDate are slow. The table currently has a clustered index on OrderID (the primary key). Which index strategy will best improve these queries?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
C. Create a nonclustered index on (CustomerID, OrderDate).
Option C is correct because creating a nonclustered index on (CustomerID, OrderDate) directly supports the query's filter (WHERE CustomerID = ?) and sort (ORDER BY OrderDate) operations. This composite index allows SQL Server to seek on CustomerID and then retrieve rows in OrderDate order without a separate sort, eliminating the need for a full clustered index scan on OrderID. It is a covering index for this query pattern, significantly reducing I/O and CPU overhead.
Key principle: Composite indexes improve queries filtering and sorting on multiple columns.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
A. Create a nonclustered index on OrderDate only.
Why it's wrong here
This index would help with ordering by OrderDate, but the query first needs to filter on CustomerID. Without an index on CustomerID, a full scan or inefficient lookup is needed.
- ✗
B. Create a filtered index on CustomerID where Status = 'Active'.
Why it's wrong here
A filtered index is limited to rows that meet a specific condition. If queries filter by CustomerID regardless of Status, this index may be incomplete and not used.
- ✓
C. Create a nonclustered index on (CustomerID, OrderDate).
Why this is correct
This composite index allows efficient seek on CustomerID and then an ordered scan of OrderDate, covering both the filter and the sort without additional operations.
Clue confirmation
The clue words "best", "primary" in the question point toward this answer.
Related concept
Composite indexes improve queries filtering and sorting on multiple columns.
- ✗
D. Create a nonclustered index on OrderID and OrderDate.
Why it's wrong here
This index does not include CustomerID, so it cannot be used to filter on CustomerID efficiently. It would not help the query.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think a single-column index on the filter column (CustomerID) or the sort column (OrderDate) is sufficient, but they miss that a composite index covering both in the correct order eliminates the need for a separate sort and key lookups, which is critical for large tables in Azure SQL Database.
Detailed technical explanation
How to think about this question
Under the hood, SQL Server's query optimizer uses index key order to satisfy both equality predicates (CustomerID) and ordering (OrderDate) in a single index seek and scan. The composite index (CustomerID, OrderDate) creates a B-tree where rows for the same CustomerID are physically sorted by OrderDate, allowing the ORDER BY to be resolved without an explicit sort operator. In a real-world scenario with millions of rows, this avoids a costly sort spill to tempdb, which can cause blocking and performance degradation under concurrent workloads.
KKey Concepts to Remember
- Composite indexes improve queries filtering and sorting on multiple columns.
- The order of columns in a composite index is crucial for performance.
- A leading column in a composite index supports efficient seeks.
- Nonclustered indexes store pointers to the clustered index or heap.
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
Composite indexes improve queries filtering and sorting on multiple columns.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Composite indexes improve queries filtering and sorting on multiple columns. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Review composite indexes improve queries filtering and sorting on multiple columns., 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 — Composite indexes improve queries filtering and sorting on multiple columns..
What is the correct answer to this question?
The correct answer is: C. Create a nonclustered index on (CustomerID, OrderDate). — Option C is correct because creating a nonclustered index on (CustomerID, OrderDate) directly supports the query's filter (WHERE CustomerID = ?) and sort (ORDER BY OrderDate) operations. This composite index allows SQL Server to seek on CustomerID and then retrieve rows in OrderDate order without a separate sort, eliminating the need for a full clustered index scan on OrderID. It is a covering index for this query pattern, significantly reducing I/O and CPU overhead.
What should I do if I get this DP-900 question wrong?
Review composite indexes improve queries filtering and sorting on multiple columns., 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: "best", "primary". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Composite indexes improve queries filtering and sorting on multiple columns.
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Last reviewed: Jun 11, 2026
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