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title: QL charts in DataLens On-premises. Overview
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  In this tutorial, you will learn about QL charts in DataLens On-premises and
  their features.
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# QL charts in DataLens On-premises. Overview


To create such charts, one uses direct queries to the source. The query is run using the source database's SQL dialect, which helps expand visualization capabilities by using database-specific transactions.


Running a query does not create a separate [dataset](../../dataset/index.md) object: a chart is generated on the fly and displayed in the preview panel.

Unlike [dataset-based charts](dataset-based-charts.md), the logic of a visualization area in QL charts favors queries against the source, i.e., the visualization area only displays the data from the query. You can also save QL charts and [add](../../operations/dashboard/add-chart.md) them to dashboards as widgets.


{% note alert %}

When using QL charts, configure access restrictions on the data source side.

{% endnote %}



QL charts:

* Reduce database workload by using direct queries.
* Are only suitable for `SELECT` queries.
* Enable the use of `JOIN`, `GROUP BY`, and `SORT BY` queries and aggregation functions in SQL queries.
* Enable the parameterization of any part of a SQL query.
* Support a limited set of [visualizations types](../../visualization-ref/index.md).


To create a QL chart, follow [this guide](../../operations/chart/create-sql-chart.md).


#### Useful links {#see-also}

* [Creating a QL chart in DataLens On-premises](../../operations/chart/create-sql-chart.md)
* [DataLens On-premises chart](../../concepts/chart/index.md)
* [Creating a chart in DataLens On-premises](../../operations/chart/create-chart.md)

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