Rollup

Summarizes values from all “child rows” that point to this row via a foreign key – the reverse of a lookup field.

When creating one, you choose:

1. the child table (any other table in the same data source),
2. its foreign key field that points back to this table,
3. the column to aggregate,
4. the aggregate function: SUM, COUNT, AVG, MIN, or MAX.

Example: an orders table with a rollup field “Total of line items” (SUM over the linked order-line-item rows).

If, instead of a single aggregated value, the child rows themselves should be visible – e.g. each individual order line item as its own row –, see Child records.

Changing the connection afterward

Via the column context menu → “Edit field” you can adjust an existing rollup field’s connection at any time, without having to delete and recreate the column. In the edit modal, in addition to field name and display format, pre-selected dropdowns appear for:

1. the child table and its foreign key field that points back to this table,
2. the column to aggregate on the child table,
3. the aggregate function (SUM, COUNT, AVG, MIN, or MAX).

All four can be changed independently of each other; clicking “Save” applies the new connection immediately.