> For the complete documentation index, see [llms.txt](https://docs-v3.toucantoco.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs-v3.toucantoco.com/data-management-in-datahub/datasets-in-toucan/preparing-data/overview-of-youprep-tm/combine/join-datasets.md). # Join datasets The Join step allows you to combine two datasets listed in the dataHub to bring columns from the former into the latter, matching rows based `on` columns correspondance ### Step parameters * `Select a dataset to join (as a right dataset)` **column(string)\***: Select a dataset to join as the right dataset. * `Select a join Type` **dropdown(string)\***`:` Choose from "left", "inner", or "left outer" join. * `left`: will keep every row of the current dataset and fill unmatched rows with `null` values, * `left outer` : * `inner`: will only keep rows that match rows of the joined dataset. * `Join based on columns:`specify 1 or more column couple(s) that will be compared to determine rows correspondance between the 2 datasets. The first element of a couple is for the current dataset column, and the second for the corresponding column in the right dataset to be joined. If you specify more than 1 couple, the matching rows will be those that find a correspondance between the 2 datasets for every column couple specified (logical ‘AND’). ### Example **Input**

Combine - join - dataset_to_join

Combine - join - dataset_to_join

**Configuration** ```json { "right_pipeline": "dataset_to_join", "type": "left", "on": [ { "id": "emp_id" } ] } ``` **Output**

Combine - join output

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