# Merge Join

## ![](/files/yAh7mkWeDXmpSgIcHx2A) Merge Join

### Description <a href="#description" id="description"></a>

The Merge Join transform performs a classic merge join between data sets with data coming from two different input transforms.

This transform assumes your data is sorted on the join keys. Use [Sort Rows](/data-shaper-1.21/knowing-the-data-shaper-designer/pipelines/transforms/sort.md) transforms on the incoming streams to enforce sorting if necessary.

Join options include INNER, LEFT OUTER, RIGHT OUTER, and FULL OUTER.

| Hop Engine | <sup>✓</sup> |
| ---------- | ------------ |
| Spark      | <sup>✓</sup> |
| Flink      | <sup>✓</sup> |
| Dataflow   | <sup>✓</sup> |

### Options

| Option           | Description                                                                                                   |
| ---------------- | ------------------------------------------------------------------------------------------------------------- |
| First Transform  | The first transform to read data from (left hand side of the join)                                            |
| Second Transform | The second transform to read data from (right hand side of the join)                                          |
| Join type        | The join type that should be used; INNER, LEFT OUTER, RIGHT OUTER, and FULL OUTER                             |
| Key Field        | The fields used for the join key, this only supports equal joins (key first transform = key second transform) |

For guidance on preventing deadlocks when using the Merge Join transform, refer to this how-to guide: [Avoiding deadlocks](/data-shaper-1.21/knowing-the-data-shaper-designer/index-5/avoiding-deadlocks.md).


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