Filter transformation in mapping data flow

  • Article
  • 04/27/2025

APPLIES TO: Azure Data Factory Azure Synapse Analytics

Data flows are available in both Azure Data Factory pipelines and Azure Synapse Analytics pipelines. This article applies to mapping data flows. If you're new to transformations, refer to the introductory article Transform data using mapping data flows.

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

Configuration

Use the data flow expression builder to enter an expression for the filter condition. To open the expression builder, select 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.

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:

Filter transformation

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

CleanData
    filter(
        year <= 1960
    ) ~> FilterBefore1960

Related content

Filter out columns with the select transformation.