Docs: Correlations (#66121)

* Add usage stats about correlations

* Add stats.correlations.count to collected stats

* Expose grafana_stat_totals_correlations metric

* Organize imports

* Correlations: Add documentation

* Add info about the feature toggle and move it to beta

* Remove incorrect bullet point

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* Update punctuation

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* Update transformation.field documentation

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docs/sources/administration/correlations/_index.md

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+---
+title: Correlations
+weight: 900
+keywords:
+  - correlations
+  - Explore
+---
+
+# Correlations
+
+You can create interactive links for Explore visualizations to run queries related to presented data by setting up Correlations.
+
+A correlation defines how data in one [data source]({{< relref "/docs/grafana/latest/datasources/" >}}) is used to query data in another data source. Some examples:
+
+- an application name returned in a logs data source can be used to query metrics related to that application in a metrics data source, or
+- a user name returned by an SQL data source can be used to query logs related to that particular user in a logs data source
+
+[Explore]({{< relref "/docs/grafana/latest/explore/" >}}) takes user-defined correlations to display links inside the visualizations. You can click on a link to run the related query and see results in [Explore Split View]({{< relref "/docs/grafana/latest/explore/#split-and-compare" >}}).
+
+Explore visualizations that currently support showing links based on correlations:
+
+- [Logs Panel]({{< relref "./use-correlations-in-visualizations#correlations-in-logs-panel">}})
+- [Table]({{< relref "./use-correlations-in-visualizations#correlations-in-table">}})
+
+You can configure correlations using [Administration > Correlation page]({{< relref "/docs/grafana/latest/administration/" >}}) or with [provisioning]({{< relref "/docs/grafana/latest/administration/provisioning" >}}).
+
+> **Note:** Correlations are available in Grafana 10.0+ as an opt-in beta feature. Modify Grafana [configuration file]({{< relref "/docs/grafana/latest/setup-grafana/configure-grafana/#configuration-file-location" >}}) to enable the `correlations` [feature toggle]({{< relref "/docs/grafana/latest/setup-grafana/configure-grafana/#feature_toggles" >}}) to use it.
+
+## Example of how links work in Explore once set up
+
+{{< figure src="/static/img/docs/correlations/correlations-in-explore-10-0.gif" caption="Correlations links in Explore" >}}
+
+See also:
+
+{{< section >}}