- A
Create a nonclustered index on CustomerID including OrderDate.
Why wrong: This index helps filter on CustomerID but does not include OrderDate in the key order, so a sort is still needed for ORDER BY OrderDate DESC.
- B
Create a nonclustered index on (CustomerID, OrderDate DESC) with included columns for other needed columns.
This covering index includes both the filter column and the sort column in the correct order, allowing efficient index seek and eliminating the need for a separate sort operation.
- C
Rebuild the clustered index to be on CustomerID.
Why wrong: Changing the clustered index to CustomerID would disrupt the primary key (OrderID) and may not improve sort performance for OrderDate. Clustered index should be on the primary key or a narrow, unique column.
- D
Create a nonclustered index on OrderDate.
Why wrong: This index helps queries that filter only on OrderDate, but it does not help filter by CustomerID, so queries with both conditions would still be inefficient.
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 can include multiple columns in their key.. 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 runs an e-commerce application on Azure SQL Database. The Orders table has millions of rows. Queries that filter on CustomerID and order by OrderDate DESC are slow. The table currently has a clustered index on OrderID (the primary key). Which indexing strategy will most improve performance for 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 index on (CustomerID, OrderDate DESC) with included columns for other needed columns.
Option B is correct because creating a nonclustered index on (CustomerID, OrderDate DESC) with included columns allows the query to filter on CustomerID and sort by OrderDate in descending order using a single index seek, avoiding a sort operation. This leverages the index's key order to directly return rows in the desired order, which is critical for performance on large tables in Azure SQL Database.
Key principle: Nonclustered indexes can include multiple columns in their key.
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 including OrderDate.
Why it's wrong here
This index helps filter on CustomerID but does not include OrderDate in the key order, so a sort is still needed for ORDER BY OrderDate DESC.
- ✓
Create a nonclustered index on (CustomerID, OrderDate DESC) with included columns for other needed columns.
Why this is correct
This covering index includes both the filter column and the sort column in the correct order, allowing efficient index seek and eliminating the need for a separate sort operation.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Nonclustered indexes can include multiple columns in their key.
- ✗
Rebuild the clustered index to be on CustomerID.
Why it's wrong here
Changing the clustered index to CustomerID would disrupt the primary key (OrderID) and may not improve sort performance for OrderDate. Clustered index should be on the primary key or a narrow, unique column.
- ✗
Create a nonclustered index on OrderDate.
Why it's wrong here
This index helps queries that filter only on OrderDate, but it does not help filter by CustomerID, so queries with both conditions would still be inefficient.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think including a column in an index (as an included column) is sufficient for sorting, but only key columns determine the physical order of rows in the index, so a nonclustered index with OrderDate as an included column cannot eliminate the need for a sort operation.
Detailed technical explanation
How to think about this question
Under the hood, SQL Server uses B-tree structures for indexes; when the index key includes (CustomerID, OrderDate DESC), the rows are stored in sorted order by CustomerID and then by OrderDate descending, allowing the query optimizer to perform an index seek on CustomerID and then a range scan to retrieve rows in the correct order without a separate sort. In Azure SQL Database, this can also reduce logical reads and improve query performance, especially when combined with included columns to cover the query and avoid key lookups.
KKey Concepts to Remember
- Nonclustered indexes can include multiple columns in their key.
- The order of columns in a nonclustered index key is critical for query optimization.
- Including `DESC` in an index key can eliminate separate sort operations for `ORDER BY DESC` clauses.
- Covering indexes (with included columns) can satisfy queries entirely from the index, avoiding table lookups.
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 can include multiple columns in their key.
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. Nonclustered indexes can include multiple columns in their key. 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 nonclustered indexes can include multiple columns in their key., 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 can include multiple columns in their key..
What is the correct answer to this question?
The correct answer is: Create a nonclustered index on (CustomerID, OrderDate DESC) with included columns for other needed columns. — Option B is correct because creating a nonclustered index on (CustomerID, OrderDate DESC) with included columns allows the query to filter on CustomerID and sort by OrderDate in descending order using a single index seek, avoiding a sort operation. This leverages the index's key order to directly return rows in the desired order, which is critical for performance on large tables in Azure SQL Database.
What should I do if I get this DP-900 question wrong?
Review nonclustered indexes can include multiple columns in their key., 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 can include multiple columns in their key.
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Last reviewed: Jun 11, 2026
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