The answer is a count of unique Windows devices per device name in the last 7 days. This is correct because the KQL query filters the `DeviceInfo` table for rows where `OperatingSystem` contains 'Windows', then uses `summarize` with `dcount(DeviceName)` to count distinct device names, and `bin(TimeGenerated, 7d)` to group results into 7-day intervals. On the Microsoft 365 Endpoint Administrator MD-102 exam, this tests your ability to interpret KQL query results for device inventory in Microsoft Sentinel, a common scenario for assessing endpoint visibility. A frequent trap is confusing `dcount` with `count`—remember that `dcount` provides an approximate distinct count, not a total row count, which is critical for accurate device inventory analysis. Memory tip: think "dcount = distinct count" and "bin = bucket in time."
MD-102 Manage and maintain devices Practice Question
This MD-102 practice question tests your understanding of manage and maintain devices. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Exhibit
{
"exhibit": "KQL query in Microsoft Sentinel: DeviceInfo | where TimeGenerated > ago(7d) | where OSPlatform == 'Windows' | summarize TotalDevices = dcount(DeviceId) by DeviceName"}
Refer to the exhibit. You run this KQL query in Microsoft Sentinel. What is the result?
{
"exhibit": "KQL query in Microsoft Sentinel: DeviceInfo | where TimeGenerated > ago(7d) | where OSPlatform == 'Windows' | summarize TotalDevices = dcount(DeviceId) by DeviceName"}
A
A list of all devices regardless of operating system.
Why wrong: Incorrect. The query filters for Windows.
B
A list of all Windows devices with their last activity.
Why wrong: Incorrect. The query does not return last activity.
C
A count of unique Windows devices per device name in the last 7 days.
Correct. The query summarizes unique devices by name.
D
A count of security alerts per device.
Why wrong: Incorrect. The query uses DeviceInfo, not alert data.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A count of unique Windows devices per device name in the last 7 days.
The KQL query uses `DeviceInfo` (a Microsoft Sentinel table for device inventory), filters with `where` to include only rows where `OperatingSystem` contains 'Windows', then uses `summarize` with `dcount(DeviceName)` to count distinct device names, and `bin(TimeGenerated, 7d)` to group by 7-day intervals. This produces a count of unique Windows devices per device name over the last 7 days, making option C correct.
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 list of all devices regardless of operating system.
Why it's wrong here
Incorrect. The query filters for Windows.
✗
A list of all Windows devices with their last activity.
Why it's wrong here
Incorrect. The query does not return last activity.
✓
A count of unique Windows devices per device name in the last 7 days.
Why this is correct
Correct. The query summarizes unique devices by name.
Related concept
Read the scenario before looking for a memorised answer.
✗
A count of security alerts per device.
Why it's wrong here
Incorrect. The query uses DeviceInfo, not alert data.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may misinterpret `dcount(DeviceName)` as a count of rows or a list of devices, rather than recognizing it as a distinct count aggregation, and may overlook that `DeviceInfo` is an inventory table, not an alert table.
Detailed technical explanation
How to think about this question
The `dcount()` function in KQL uses the HyperLogLog algorithm to estimate distinct counts efficiently, which is ideal for large datasets where exact counts are expensive. The `bin(TimeGenerated, 7d)` creates fixed 7-day time buckets, so the result shows distinct device counts per 7-day window, not a rolling 7-day count. In real-world scenarios, this query helps track Windows device churn or new device onboarding trends over weekly intervals.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this MD-102 question in full detail.
Manage and maintain devices — This question tests Manage and maintain devices — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A count of unique Windows devices per device name in the last 7 days. — The KQL query uses `DeviceInfo` (a Microsoft Sentinel table for device inventory), filters with `where` to include only rows where `OperatingSystem` contains 'Windows', then uses `summarize` with `dcount(DeviceName)` to count distinct device names, and `bin(TimeGenerated, 7d)` to group by 7-day intervals. This produces a count of unique Windows devices per device name over the last 7 days, making option C correct.
What should I do if I get this MD-102 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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