If you are wrangling datasets that represent transactional or serialized data, you can append together slices of data to build a larger dataset for richer analysis. For example, you are cleansing log messages on a weekly basis. You can create separate datasets for each day's log messages and then bring them altogether into a single dataset for processing through a single recipe. This method works best for datasets that have identical or very similar structures.

Below, you can see two datasets of contact information. These simplified datasets track customer contact records.

Dataset01:

Dataset02:

Notes:

• There is one overlapping record for Tina Toms.
• There is a mismatch in one column name ("Last Contact" vs. "Last Contact Date").
• The columns are in a different order.

Steps:

1. Load your first dataset (Dataset01) .
2. In the recipe panel, add a step. In the Transformation textbox, enter union.
3. In the Union page, you bring together two or more datasets based on a shared set of fields. 
   1. A union operation appends datasets together. For more information, see Union Page.
4. To add another dataset, click Add datasets. Navigate to select the file to add to the union (Dataset02).
5. Initially, fields are mapped based on the column names. However, in this example, the Last_Contact_Date field from Dataset02 is not included. You can:
   1. Click the + icon next to the Last_Contact_Date field in the left panel. The field is added as a separate field. However, it is not matched with the other contact date field from the original dataset.

   2. From the Match columns drop-down menu, select By Position. In this case, you can see that there are only three fields, but the order is mismatched.

      Tip: When possible, you should try to rename or align columns in your datasets prior to building a union transform step. Otherwise, you might have to edit the columns after the union has been completed.  To rename a column, click Rename from the column drop-down in the Transformer page. You can use the same drop-down to move a column.

6. In this case, you can cancel the union and reposition the Email column after the Last Contact column in Dataset01. 
7. Then, open the Union page again and add Dataset02. Select By Position from the Match columns drop-down menu. Your columns are matched.
8. Click Add to Recipe.

Dataset02 records have now been added to Dataset01, which now contains all of the records from both datasets. Note that the record for Tina Toms appears twice in the appended dataset.

• If the appended dataset is a record of all contacts, you should leave the duplicate record in place.
• If the appended dataset is a record of the most recent contact with each customer, you should remove the duplicate record. For more information, see Deduplicate Data.