Join Collections — Reference

Enrich each left-hand record with fields from the first matching right-hand record.

Before you begin

• A Server Connect action with the input collection available from an earlier step.

Join Collections

Enrich each left-hand record with fields from the first matching right-hand record.

Settings

Setting	Meaning
Name	Names the joined collection.
Collection 1	The left collection. The result preserves one output record for each of its records, including records with no match.
Collection 2	The lookup collection. Only its first matching record is merged into a given left record.
Match Columns	Mappings from left field names to right field names. For example, category_id → id matches a product’s category to a category record.
Match All	When enabled, every mapped comparison must match. When disabled, any mapped comparison is sufficient. Comparisons in the installed implementations use equality with coercion; keep key types consistent.

Worked example

Join [{“name”:“Notebook”,“category_id”:2}] with [{“id”:2,“category”:“Stationery”}] using category_id → id. The result contains the product fields plus id and category from the lookup record. Add an unmatched product and confirm it remains in the result.

Check the output shape

This is not a SQL join that emits every matching pair. Duplicate matches in Collection 2 use the first one. Right-hand fields overwrite same-named left fields; rename conflicting columns first. The operation returns new records and does not update either source or the database.

Use the transformed result

Bind later server steps to the Name of this transformation. To show the result on a page, return the intended fields from the action and load that response with App Connect.

Check your result

You can predict the resulting record shape and verify it before binding or returning the data.