Question 179 of 982

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

Quick Answer

The correct approach is to change the clustered key to an integer IDENTITY column while keeping a nonclustered index on TransactionID. This works because a clustered index on a GUID column causes random insert order and excessive page splits, severely degrading insert performance in Azure SQL Database. By switching to a monotonically increasing integer as the clustered key, new rows are appended sequentially, eliminating fragmentation and dramatically improving throughput. The nonclustered index on TransactionID then preserves fast point lookups by providing a separate, efficient search path. On the DP-900 exam, this scenario tests your understanding of how clustered indexes physically organize data and why sequential keys outperform random ones for write-heavy workloads. A common trap is assuming a GUID clustered index is fine because it supports unique lookups, but the exam emphasizes that insert performance suffers from fragmentation. Remember the memory tip: "GUIDs scatter, INTs gather"—a sequential integer clusters data tightly, while a GUID scatters it across pages, causing splits.

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 maintains a large 'Transactions' table in Azure SQL Database. The table has a clustered index on a GUID column (TransactionID). Over time, they observe slow insert performance due to index fragmentation and page splits. They also need fast point lookups by TransactionID. Which approach should they take to improve insert performance while still supporting fast lookups?

Question 1mediummultiple choice

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A
Change the clustered index to a nonclustered index on TransactionID and make the table a heap
Why wrong: While this avoids GUID fragmentation, heaps can lead to performance degradation for queries that need to scan or sort data. Also, point lookups via a nonclustered index on a heap require extra key lookups (RID lookups), which are less efficient than clustered index seeks.
B
Change the clustered key to an integer IDENTITY column and keep a nonclustered index on TransactionID
An integer IDENTITY column provides sequential values that reduce fragmentation and page splits, improving insert performance. The nonclustered index on TransactionID supports efficient point lookups. This is a recommended pattern when the natural key is not ideal for clustering.
C
Keep the clustered index on TransactionID but rebuild it daily
Why wrong: Rebuilding the index daily does not prevent fragmentation from occurring during inserts throughout the day. The underlying issue of random GUID inserts causing page splits remains, and frequent rebuilds incur overhead.
D
Remove the clustered index entirely and create a nonclustered index on TransactionID
Why wrong: This makes the table a heap, which can cause performance issues for range queries and other operations. Sequential insert performance may improve slightly, but point lookups require a nonclustered index followed by a RID lookup, which is slower than a clustered index seek. Also, heaps can suffer from high fragmentation over time.

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

✓

Change the clustered key to an integer IDENTITY column and keep a nonclustered index on TransactionID

Option B is correct because using an integer IDENTITY column as the clustered key eliminates the random insertion order and page splits caused by a GUID clustered index, while the nonclustered index on TransactionID provides fast point lookups. In Azure SQL Database, a clustered index determines the physical order of data; a monotonically increasing integer avoids fragmentation and improves insert throughput.

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.

✗
Change the clustered index to a nonclustered index on TransactionID and make the table a heap
Why it's wrong here
While this avoids GUID fragmentation, heaps can lead to performance degradation for queries that need to scan or sort data. Also, point lookups via a nonclustered index on a heap require extra key lookups (RID lookups), which are less efficient than clustered index seeks.
✓
Change the clustered key to an integer IDENTITY column and keep a nonclustered index on TransactionID
Why this is correct
An integer IDENTITY column provides sequential values that reduce fragmentation and page splits, improving insert performance. The nonclustered index on TransactionID supports efficient point lookups. This is a recommended pattern when the natural key is not ideal for clustering.
Related concept
Read the scenario before looking for a memorised answer.
✗
Keep the clustered index on TransactionID but rebuild it daily
Why it's wrong here
Rebuilding the index daily does not prevent fragmentation from occurring during inserts throughout the day. The underlying issue of random GUID inserts causing page splits remains, and frequent rebuilds incur overhead.
✗
Remove the clustered index entirely and create a nonclustered index on TransactionID
Why it's wrong here
This makes the table a heap, which can cause performance issues for range queries and other operations. Sequential insert performance may improve slightly, but point lookups require a nonclustered index followed by a RID lookup, which is slower than a clustered index seek. Also, heaps can suffer from high fragmentation over time.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates assume rebuilding the clustered index (Option C) is a sufficient maintenance fix, but the DP-900 exam tests understanding that the root cause is the choice of clustered key data type, not just fragmentation management.

Detailed technical explanation

How to think about this question

Under the hood, a GUID clustered index causes page splits because new rows are inserted at random pages, forcing SQL Server to split full pages and move data, leading to fragmentation and wasted space. An integer IDENTITY column, when used as the clustered key, ensures new rows are appended to the end of the index, minimizing page splits and maintaining a dense, sequential fill factor. The nonclustered index on TransactionID stores the clustered key (the integer) as the row locator, enabling efficient key lookups without the overhead of a heap's RID.

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 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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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: Change the clustered key to an integer IDENTITY column and keep a nonclustered index on TransactionID — Option B is correct because using an integer IDENTITY column as the clustered key eliminates the random insertion order and page splits caused by a GUID clustered index, while the nonclustered index on TransactionID provides fast point lookups. In Azure SQL Database, a clustered index determines the physical order of data; a monotonically increasing integer avoids fragmentation and improves insert throughput.

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.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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