data.join

data.join combines two tables by matching rows on key fields. It takes two Table inputs (left and right ports) and produces one Table output containing columns from both sides.

Input: Table (left port), Table (right port) Output: Table

Basic config

nodes:
  orders-with-customers:
    type: data.join
    config:
      join_type: left
      left_key: customer_id
      right_key: id

Config reference

Field	Type	Required	Description
join_type	string	no	Join type: inner, left, right, full (default: inner)
left_key	string	yes	Column name on the left table to join on
right_key	string	yes	Column name on the right table to join on
right_prefix	string	no	Prefix for right-side columns to avoid name collisions

Output schema

The output contains all columns from the left table plus all columns from the right table (excluding the right join key, which would duplicate the left key). When both tables share a column name, use right_prefix to disambiguate.

nodes:
  merged:
    type: data.join
    config:
      join_type: inner
      left_key: id
      right_key: order_id
      right_prefix: "order_"

With right_prefix: "order_", right-side columns status and total become order_status and order_total in the output.

Join types

Inner join

Returns only rows with matching keys on both sides.

nodes:
  matched-orders:
    type: data.join
    config:
      join_type: inner
      left_key: id
      right_key: customer_id

edges:
  - customers.output -> matched-orders.left
  - orders.output -> matched-orders.right

Left join

Returns all rows from the left table. Right-side columns are null when no match exists.

nodes:
  all-customers:
    type: data.join
    config:
      join_type: left
      left_key: id
      right_key: customer_id

Right join

Returns all rows from the right table. Left-side columns are null when no match exists.

nodes:
  all-orders:
    type: data.join
    config:
      join_type: right
      left_key: id
      right_key: customer_id

Full join

Returns all rows from both tables. Columns are null on the side where no match exists.

nodes:
  full-merge:
    type: data.join
    config:
      join_type: full
      left_key: email
      right_key: email

Pipeline example

nodes:
  load-orders:
    type: file.csv
    config:
      path: orders.csv

  load-products:
    type: file.csv
    config:
      path: products.csv

  orders-enriched:
    type: data.join
    config:
      join_type: left
      left_key: product_id
      right_key: id
      right_prefix: "product_"

  summary:
    type: data.map
    config:
      include_original: true
      fields:
        line_total: "{{ quantity * product_price }}"

edges:
  - load-orders.output -> orders-enriched.left
  - load-products.output -> orders-enriched.right
  - orders-enriched.output -> summary.input

This pipeline joins orders with product data, then computes a line total using the product price from the right table.