> ## Documentation Index > Fetch the complete documentation index at: https://www.integrate.io/docs/llms.txt > Use this file to discover all available pages before exploring further. # ETL: Union Transformation > Use the Union transformation to merge records from two inputs with identical schemas into a single output stream in your ETL data pipeline. Union component in the pipeline designer **Note:** Union in Integrate.io ETL acts like Union all in SQL (will not remove duplicate rows) ## Union inputs Select 2 inputs and drag and drop the component menu button onto the union component: Dragging two inputs onto the Union component Within the component you can define which input is the left input and which is the right input. ## Input field mapping Map the pairs of fields from the two inputs into a single output field. You can auto-fill the list by order of fields in the two inputs (Auto-fill by order) or by matching field names (Auto-fill by name). You can also manually pick pairs of fields from the two inputs. Input field mapping with auto-fill by order and by name options