Join

Combine two datasets horizontally based on matching key columns.

Sockets

Inputs

Socket	Direction	Description
L (input-left)	Input	Left dataset
R (input-right)	Input	Right dataset

Outputs

Socket	Direction	Description
L (output-left)	Output	Unmatched rows from left (left anti-join)
J (output-match)	Output	Matched/joined rows (inner join)
R (output-right)	Output	Unmatched rows from right (right anti-join)

Configuration

Option	Description
Left Key	Column(s) from left input to match on
Right Key	Column(s) from right input to match on
Right Suffix	Suffix for right columns that conflict with left (default: _right)

How It Works

The Join tool performs three operations simultaneously:

1. Inner Join (J output): Rows where keys match between left and right
2. Left Anti-Join (L output): Rows from left with no match in right
3. Right Anti-Join (R output): Rows from right with no match in left

This gives you complete visibility into what matched and what didn't.

Key Configuration

Single Key

Match on one column from each side:

Left Key	Right Key
customer_id	id

Multiple Keys

Match on multiple columns (composite key):

Left Key	Right Key
year	year
month	month

Keys are matched in order - first left key matches first right key, etc.

No Keys (Cross Join)

If no keys are specified, a cross join is performed - every row from left is combined with every row from right. Use with caution on large datasets!

Column Handling

Key Columns

Key columns from the right input are excluded from the joined output (J socket) to avoid duplication. The left key columns are included.

Conflicting Column Names

If left and right have non-key columns with the same name, the right column is renamed with the suffix (default _right):

• Left has: id, value
• Right has: id, value
• Joined on id
• Output: id, value, value_right

You can customize the suffix in configuration.

Examples

Basic Join

Match orders to customers:

Left (Orders):

order_id	customer_id	amount
1	101	50
2	102	75
3	103	25

Right (Customers):

id	name
101	Alice
102	Bob

Configuration:

• Left Key: customer_id
• Right Key: id

J Output (Matched):

order_id	customer_id	amount	name
1	101	50	Alice
2	102	75	Bob

L Output (Unmatched Left):

order_id	customer_id	amount
3	103	25

R Output (Unmatched Right): (empty - all customers had orders)

Finding Missing Data

Use the L and R outputs to find records that don't have matches:

• L output: "Orders without customers"
• R output: "Customers without orders"

Notes

• Key types should match: Join works best when key columns have the same type. Cast if needed.
• Null keys: Rows with null keys will not match (nulls never equal other values in joins)
• Performance: Joins on indexed or sorted columns are faster
• Memory: Large cross joins can produce massive results

Related

• Select - Cast types or rename columns before joining
• Filter - Filter results after joining