Join sheets by column

Join sheets by column merges two sheets side by side based on matching values in a key column from each side, similar to a SQL join. If you configure a Right list prefix, columns from the right sheet are prefixed in the output to avoid naming conflicts.

Availability: GA

What it does

Input: one or more CSV lists — typically a "left" sheet and a "right" sheet that share a common key.
Output: a single CSV file where each row combines a left-sheet row with the matching right-sheet row(s), based on the configured key columns. Right-sheet columns are prefixed only if a Right list prefix is configured; by default, the prefix is empty and right-sheet columns keep their original names.

When to use it

You need to enrich one file with columns from another, such as adding customer details to an orders file.
Two upstream sources send related data separately (for example, a header file and a details file) and you need to combine them by a shared ID.
You want to look up reference data (like product names) using an ID column before validation.

How to configure it

In the MFF builder, add a Join sheets by column node after the node(s) that produce the left and right sheets.

Settings

Setting	Description	Default
Left key column	The column in the left sheet used to match rows against the right sheet.	Empty
Right key column	The column in the right sheet used to match rows against the left sheet.	Empty
Right list prefix	The prefix added to every column name coming from the right sheet, to avoid collisions with left-sheet column names.	Empty
Output file name	The file name given to the joined output file.	Empty

Example

Input

Left sheet orders.csv: OrderId, CustomerId, Amount
Right sheet customers.csv: CustomerId, Name, Region

With Left key column = CustomerId, Right key column = CustomerId, and Right list prefix = customer_.

Output

OrderId	CustomerId	Amount	customer_Name	customer_Region
1001	55	250.00	Acme Co	West

Troubleshooting

Rows are missing after the join

Join sheets by column only keeps rows where the key columns match on both sides. Check for typos, extra whitespace, or type mismatches (for example, "55" vs 55) between the key columns.

Output has unexpected duplicate-looking columns

Set a distinct Right list prefix so right-sheet columns don't collide with left-sheet columns of the same name.