Question 375 of 982

Identify considerations for relational data on Azure →mediumMultiple ChoiceObjective-mapped

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 platform. The 'Orders' table has millions of rows with columns OrderID (primary key), CustomerID, OrderDate, and TotalAmount. Queries often filter by CustomerID (equality) and OrderDate (range). Currently, these queries are slow. Which index should be created to improve performance?

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.

Question 1mediummultiple choice

Full question →

A
A nonclustered index on OrderID
Why wrong: An index on OrderID does not help queries filtering by CustomerID and OrderDate. The primary key already has a clustered index on OrderID, which is used for lookups by OrderID.
B
A nonclustered index on (CustomerID, OrderDate)
This composite index covers the query predicate perfectly. CustomerID is the equality column, and OrderDate is the range column. The index allows the database engine to efficiently locate rows for a specific customer and then scan a small range of dates.
C
A nonclustered index on OrderDate
Why wrong: Indexing only OrderDate would not help the CustomerID filter. The database would still need to scan all rows for the requested customer after filtering by date.
D
A clustered index on CustomerID
Why wrong: The table already has a clustered index on OrderID (the primary key). You cannot have more than one clustered index on a table. Rebuilding the clustered index on CustomerID would change the physical order of rows and may affect other queries.

Full breakdown with real-world context →

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

✓

A nonclustered index on (CustomerID, OrderDate)

The query pattern filters by CustomerID (equality) and OrderDate (range). A composite nonclustered index on (CustomerID, OrderDate) allows SQL Database to seek directly to the matching CustomerID rows and then efficiently scan the ordered OrderDate range within that partition, avoiding a full table scan or key lookup. This index order leverages the index's B-tree structure for both equality and range predicates.

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.

✗
A nonclustered index on OrderID
Why it's wrong here
An index on OrderID does not help queries filtering by CustomerID and OrderDate. The primary key already has a clustered index on OrderID, which is used for lookups by OrderID.
✓
A nonclustered index on (CustomerID, OrderDate)
Why this is correct
This composite index covers the query predicate perfectly. CustomerID is the equality column, and OrderDate is the range column. The index allows the database engine to efficiently locate rows for a specific customer and then scan a small range of dates.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
A nonclustered index on OrderDate
Why it's wrong here
Indexing only OrderDate would not help the CustomerID filter. The database would still need to scan all rows for the requested customer after filtering by date.
✗
A clustered index on CustomerID
Why it's wrong here
The table already has a clustered index on OrderID (the primary key). You cannot have more than one clustered index on a table. Rebuilding the clustered index on CustomerID would change the physical order of rows and may affect other queries.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often choose a single-column index on OrderDate (Option C) thinking it covers the range filter, but they overlook that without CustomerID as the leading key, the index cannot efficiently narrow down to a specific customer, resulting in a full index scan instead of a seek.

Detailed technical explanation

How to think about this question

In Azure SQL Database, a composite index with the equality column first (CustomerID) and the range column second (OrderDate) enables a single index seek on CustomerID followed by a range scan on OrderDate within the leaf pages. This is because B-tree indexes store rows in key order; placing the range column second allows the database engine to use the index's ordering to efficiently locate the start and end of the date range without scanning unrelated rows. In real-world e-commerce platforms, this pattern is critical for reports like 'orders by customer in the last month' where millions of rows exist.

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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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: A nonclustered index on (CustomerID, OrderDate) — The query pattern filters by CustomerID (equality) and OrderDate (range). A composite nonclustered index on (CustomerID, OrderDate) allows SQL Database to seek directly to the matching CustomerID rows and then efficiently scan the ordered OrderDate range within that partition, avoiding a full table scan or key lookup. This index order leverages the index's B-tree structure for both equality and range predicates.

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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