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Use Kusto Query Language (KQL) in Azure Monitor Logs to investigate telemetry, isolate errors and identify patterns. In the Azure portal, Log Analytics is where you write and run those queries. Results are near-real-time—not necessarily immediate: resource logs can take several minutes to become queryable.
What KQL and Log Analytics each do
KQL is the language; Azure Monitor Logs is the data platform; and Log Analytics is the Azure portal experience for authoring, running and inspecting queries. A KQL query is a read-only request that processes data and returns results. Those results can support troubleshooting, analysis, alerts, dashboards and reports. Microsoft’s Azure Monitor Logs overview and log query overview explain the platform and language.
“Real-time” needs qualification: retrieval is near-real-time, and resource log data may take several minutes to appear. In its sample resource-log workflow, Microsoft says to expect rows within about 10 minutes of generating data. That is tutorial guidance, not a universal latency guarantee or service-level commitment. The resource-log tutorial describes that example.
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Choose the right query experience
Log Analytics offers KQL mode and Simple mode. KQL mode gives direct control over the query, making it useful when you know the table and need precise filters, projections or aggregations. Simple mode offers point-and-click filtering and analysis, which can suit users who are not yet comfortable writing KQL. Both work within Azure Monitor; the choice depends on the task and the operator’s familiarity with the language. The Log Analytics overview describes the experience.
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Build a diagnostic query from a table outward
Start with a table that contains the telemetry you need, then narrow it. Microsoft recommends table-first queries to make scope clear and help performance. Broad search queries can be slower; if you know the relevant column, filter that column instead. A table named in an example may not exist in your workspace, so verify your available data and schema before adapting it.
- Set scope. Open Logs from the workspace for workspace-level data, or from a specific resource for that resource’s context. If the investigation spans resources, use Azure Monitor or a workspace-level query where you have access.
- Confirm the table and fields. Check the schema and available tables for the resource. Microsoft’s data reference maps resource log categories to Log Analytics tables: Azure Monitor data reference.
- Inspect a small sample. Enter the table name and use
taketo inspect records and column names. Microsoft’s getting-started example isSecurityEvent | take 10; it is illustrative, and the table may not be enabled or populated in your workspace. - Add time and field filters. Use a time range appropriate to the incident, then add
whereconditions for fields you know. Check table and column spelling and casing against the schema. - Return only useful columns. Use projection to focus the results on fields needed for diagnosis. Summarize or aggregate when you are looking for trends, concentrations or outliers rather than individual records.
- Refine and reuse. Inspect the results, adjust the filters or aggregation, and, when useful, reuse the query in a workbook or alert.
Microsoft’s getting-started guidance includes table-first examples, while the query overview covers Azure Monitor’s KQL support.
Diagnose an empty or incomplete result
Check whether the query has the right scope
Logs opened from an individual resource may not show other resources’ data. For a cross-resource investigation, query from Azure Monitor or the workspace instead, subject to your access. The Log Analytics overview explains the difference between resource and workspace contexts.
Allow time for ingestion
Resource logs may take several minutes to appear. If you have just generated test data, wait and run the query again; Microsoft’s resource-log tutorial uses about 10 minutes as an expectation for its sample workflow, not a guaranteed maximum. See the tutorial’s timing guidance.
Verify permissions
Querying requires workspace query-read permissions, including Microsoft.OperationalInsights/workspaces/query/*/read. Microsoft lists Log Analytics Reader as an example role. If access is denied or results are restricted, ask an administrator to confirm your role and workspace access. Microsoft’s query getting-started page describes the permission requirement.
Confirm the table and schema
A resource’s logs do not necessarily land in the table you expect. Check the resource category and corresponding Log Analytics table in the Azure Monitor data reference, then confirm the table contains records for the period you are querying.
Account for Azure Monitor’s KQL differences
Azure Monitor supports a subset of KQL, with differences from Azure Data Explorer. A query copied from another Kusto service may use a statement, function or operator that Azure Monitor does not support. Check the Azure Monitor log query overview before troubleshooting syntax that works elsewhere.
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Use examples and references without assuming your workspace matches
Log Analytics includes more than 500 curated example queries, according to Microsoft’s query documentation, and the collection continues to grow. Treat them as starting points: examples depend on particular tables and fields, which may not be present or populated in your workspace. Browse Use queries in Log Analytics, then check the KQL tutorials and language reference when you need to adapt syntax.
Security requirement for query API clients
Since July 1, 2025, querying log data and events through the Log Analytics or Application Insights query API endpoints requires TLS 1.2 or higher, according to Microsoft. This requirement is specifically about those API endpoints; do not treat it as a statement about every way of accessing Azure Monitor. Check the current log query documentation when configuring API clients.
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