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# Beam SQL: Overview

Beam SQL allows a Beam user (currently only available in Beam Java) to query
bounded and unbounded `PCollections` with SQL statements. Your SQL query
is translated to a `PTransform`, an encapsulated segment of a Beam pipeline.
You can freely mix SQL `PTransforms` and other `PTransforms` in your pipeline.

There are three main things you will need to know to use SQL in your pipeline:

 - [Apache Calcite](http://calcite.apache.org): a widespread SQL dialect used in
   big data processing with some streaming enhancements. Calcite provides the
   basic dialect underlying Beam SQL. We have added additional extensions to
   make it easy to leverage Beam's unified batch/streaming model and support
   for complex data types.
 - [SqlTransform](https://beam.apache.org/releases/javadoc/{{ site.release_latest }}/index.html?org/apache/beam/sdk/extensions/sql/SqlTransform.html): 
   the interface for creating `PTransforms` from SQL queries.
 - [Row](https://beam.apache.org/releases/javadoc/{{ site.release_latest }}/index.html?org/apache/beam/sdk/values/Row.html):
   the type of elements that Beam SQL operates on. A `PCollection<Row>` plays the role of a table.

The [SQL pipeline walkthrough]({{ site.baseurl
}}/documentation/dsls/sql/walkthrough) works through how you use
these.

