Question 245 of 953

Monitor, configure, and optimize database resources →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is to update all statistics on the table. This is correct because a clustered index scan on a large table often indicates that the query optimizer is working with stale distribution statistics, causing it to underestimate the selectivity of the query and choose a full scan over a more efficient seek or range operation. By updating all statistics, you refresh the histogram and density information, giving the optimizer the data it needs to potentially select a plan that avoids the scan and reduces execution time. On the Microsoft Azure Database Administrator Associate DP-300 exam, this scenario tests your understanding of query tuning fundamentals without structural changes—a common trap is immediately assuming you need a new index, but the question explicitly prohibits that. Remember the memory tip: “Stale stats scan, fresh stats seek.”

DP-300 Practice Question: Monitor, configure, and optimize database resources

This DP-300 practice question tests your understanding of monitor, configure, and optimize database resources. 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.

You are managing an Azure SQL Database that runs a critical line-of-business application. Users report that a specific query is running slower than usual. You identify that the query is performing a clustered index scan on a large table with over 10 million rows. The table has a clustered index on an identity column and a nonclustered index on a frequently filtered column. You need to minimize the query execution time without adding additional indexes. What should you do?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.

Question 1mediummultiple choice

Full question →

A
Increase the service tier of the Azure SQL Database to provide more resources.
Why wrong: Increasing resources might improve performance but does not address the root cause of the suboptimal plan; the scan may still occur.
B
Update all statistics on the table.
Updating statistics helps the query optimizer generate a more accurate cardinality estimate, which may lead to an index seek instead of a scan.
C
Rebuild the clustered index to reduce fragmentation.
Why wrong: Rebuilding the clustered index can reduce fragmentation but does not guarantee a change from scan to seek if the query predicate is not selective.
D
Update the statistics on the nonclustered index only.
Why wrong: Updating only the nonclustered index statistics may not affect the decision to use the clustered index scan if the query predicate does not filter on that index's key columns.

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

✓

Update all statistics on the table.

The query is performing a clustered index scan, which means SQL Server is reading all rows in the table. Outdated statistics can cause the optimizer to choose a scan instead of a more efficient seek. Updating all statistics on the table (option B) provides the optimizer with fresh distribution information, potentially allowing it to choose a better execution plan that avoids the scan, thereby reducing query execution time without adding 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.

✗
Increase the service tier of the Azure SQL Database to provide more resources.
Why it's wrong here
Increasing resources might improve performance but does not address the root cause of the suboptimal plan; the scan may still occur.
✓
Update all statistics on the table.
Why this is correct
Updating statistics helps the query optimizer generate a more accurate cardinality estimate, which may lead to an index seek instead of a scan.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Rebuild the clustered index to reduce fragmentation.
Why it's wrong here
Rebuilding the clustered index can reduce fragmentation but does not guarantee a change from scan to seek if the query predicate is not selective.
✗
Update the statistics on the nonclustered index only.
Why it's wrong here
Updating only the nonclustered index statistics may not affect the decision to use the clustered index scan if the query predicate does not filter on that index's key columns.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often assume a scan is always due to fragmentation (option C) or resource constraints (option A), when in fact the most common cause is stale statistics leading to a poor execution plan choice.

Detailed technical explanation

How to think about this question

Statistics in SQL Server store histograms and density information about index key values. When statistics are stale, the cardinality estimator may misestimate row counts, leading to an incorrect plan (e.g., a scan when a seek is more efficient). Updating statistics with FULLSCAN or a high sample rate can dramatically improve cardinality estimates. In this scenario, the nonclustered index on the frequently filtered column may be the better path, but without updated statistics, the optimizer may not trust it.

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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.

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-300 question test?

Monitor, configure, and optimize database resources — This question tests Monitor, configure, and optimize database resources — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Update all statistics on the table. — The query is performing a clustered index scan, which means SQL Server is reading all rows in the table. Outdated statistics can cause the optimizer to choose a scan instead of a more efficient seek. Updating all statistics on the table (option B) provides the optimizer with fresh distribution information, potentially allowing it to choose a better execution plan that avoids the scan, thereby reducing query execution time without adding indexes.

What should I do if I get this DP-300 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: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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