- A
Create a nonclustered index on OrderID only
Why wrong: OrderID is already the clustered index, so another index on OrderID would be redundant and would not help because the query filters on OrderDate and CustomerID, not OrderID.
- B
Create separate nonclustered indexes on OrderDate and CustomerID
Why wrong: Separate indexes allow the database to use either one, but not both simultaneously in an efficient way. The optimizer may use one index and then perform lookups, which is less efficient than a composite index that covers both columns.
- C
Create a nonclustered composite index on (OrderDate, CustomerID)
A composite index on both columns allows the database to find rows matching both filter conditions in a single index seek. This is the most efficient strategy for queries that filter on multiple columns together.
- D
Create a clustered index on CustomerID instead of OrderID
Why wrong: Changing the clustered index would reorganize the entire table and might improve some queries, but OrderID is likely used for joins and lookups. Moreover, a clustered index on CustomerID would not directly benefit the filter on OrderDate. A nonclustered composite index is less disruptive and more targeted.
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. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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 system. The Orders table has millions of rows with a clustered index on OrderID (the primary key). Queries that filter on OrderDate and CustomerID to find recent orders for a specific customer are very slow. Which indexing strategy will most improve the performance of these queries?
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 composite index on (OrderDate, CustomerID)
The query filters on both OrderDate and CustomerID, so a composite nonclustered index on (OrderDate, CustomerID) allows SQL Server to perform a single index seek to locate the matching rows without touching the clustered index until the final key lookup. This dramatically reduces I/O compared to scanning the entire clustered index or using multiple separate indexes.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 OrderID only
Why it's wrong here
OrderID is already the clustered index, so another index on OrderID would be redundant and would not help because the query filters on OrderDate and CustomerID, not OrderID.
- ✗
Create separate nonclustered indexes on OrderDate and CustomerID
Why it's wrong here
Separate indexes allow the database to use either one, but not both simultaneously in an efficient way. The optimizer may use one index and then perform lookups, which is less efficient than a composite index that covers both columns.
- ✓
Create a nonclustered composite index on (OrderDate, CustomerID)
Why this is correct
A composite index on both columns allows the database to find rows matching both filter conditions in a single index seek. This is the most efficient strategy for queries that filter on multiple columns together.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Create a clustered index on CustomerID instead of OrderID
Why it's wrong here
Changing the clustered index would reorganize the entire table and might improve some queries, but OrderID is likely used for joins and lookups. Moreover, a clustered index on CustomerID would not directly benefit the filter on OrderDate. A nonclustered composite index is less disruptive and more targeted.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think separate indexes on each filter column are sufficient, not realizing that a composite index is far more efficient for queries that filter on multiple columns together, because it avoids the need for index intersection or multiple lookups.
Detailed technical explanation
How to think about this question
A composite index stores the key columns in the order specified, so (OrderDate, CustomerID) enables a seek on OrderDate and then a residual predicate on CustomerID within the same index page range. SQL Server's query optimizer can use index intersection with multiple single-column indexes, but this requires a hash match or merge join of two B-tree structures, which is more CPU- and I/O-intensive than a single composite index seek. In a real-world e-commerce system with millions of rows, the difference can be orders of magnitude in query response time.
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.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Identify considerations for relational data on Azure — study guide chapter
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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 — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a nonclustered composite index on (OrderDate, CustomerID) — The query filters on both OrderDate and CustomerID, so a composite nonclustered index on (OrderDate, CustomerID) allows SQL Server to perform a single index seek to locate the matching rows without touching the clustered index until the final key lookup. This dramatically reduces I/O compared to scanning the entire clustered index or using multiple separate indexes.
What should I do if I get this DP-900 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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