# UNION


Combines the rows from two or more datasets into a single result.

**Parameters**
+ `datasetsColumns` — A JSON-encoded string representing a list of all the columns in the datasets.
+ `secondaryDatasetNames` — A JSON-encoded string representing a list of one or more secondary datasets.
+ `secondaryInputs` — A JSON-encoded string representing a list of Amazon S3 buckets and object key names that tell DataBrew where to find the secondary dataset(s).
+ `targetColumnNames` — A JSON-encoded string representing a list of column names for the results.

**Example**  
  

```
{
    "Action": {
        "Operation": "UNION",
        "Parameters": {
            "datasetsColumns": "[[\"assembly_session\",\"state_code\",\"state_name\",\"year\",\"all_votes\",\"yes_votes\",\"no_votes\",\"abstain\",\"idealpoint_estimate\",\"affinityscore_usa\",\"affinityscore_russia\",\"affinityscore_china\",\"affinityscore_india\",\"affinityscore_brazil\",\"affinityscore_israel\"],[\"assembly_session\",\"state_code\",\"state_name\",null,null,null,null,null,null,null,null,null,null,null,null]]",
            "secondaryDatasetNames": "[\"votes\"]",
            "secondaryInputs": "[{\"S3InputDefinition\":{\"Bucket\":\"databrew-public-datasets-us-east-1\",\"Key\":\"votes.csv\"}}]",
            "targetColumnNames": "[\"assembly_session\",\"state_code\",\"state_name\",\"year\",\"all_votes\",\"yes_votes\",\"no_votes\",\"abstain\",\"idealpoint_estimate\",\"affinityscore_usa\",\"affinityscore_russia\",\"affinityscore_china\",\"affinityscore_india\",\"affinityscore_brazil\",\"affinityscore_israel\"]"
        }
    }
}
```