data-flow-filter.md

title	titleSuffix	description	author	ms.author	ms.reviewer	ms.service	ms.subservice	ms.topic	ms.custom	ms.date
Filter transformation in mapping data flow	Azure Data Factory & Azure Synapse	Filter out rows using the filter transformation in a mapping data flow in Azure Data Factory or Synapse Analytics.	kromerm	makromer	daperlov	data-factory	data-flows	conceptual	synapse	09/09/2021

Filter transformation in mapping data flow

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The Filter transforms allows row filtering based upon a condition. The output stream includes all rows that matching the filtering condition. The filter transformation is similar to a WHERE clause in SQL.

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Configuration

Use the data flow expression builder to enter an expression for the filter condition. To open the expression builder, click on the blue box. The filter condition must be of type boolean. For more information on how to create an expression, see the expression builder documentation.

:::image type="content" source="media/data-flow/filter1.png" alt-text="Filter transformation":::

Data flow script

Syntax

<incomingStream>
    filter(
        <conditionalExpression>
    ) ~> <filterTransformationName>

Example

The below example is a filter transformation named FilterBefore1960 that takes in incoming stream CleanData. The filter condition is the expression year <= 1960.

In the UI, this transformation looks like the below image:

:::image type="content" source="media/data-flow/filter1.png" alt-text="Filter transformation":::

The data flow script for this transformation is in the snippet below:

CleanData
    filter(
        year <= 1960
    ) ~> FilterBefore1960

Next steps

Filter out columns with the select transformation