Sum of a Column from one table to another

Hey,

So I have three tables, Sales, Purchases & Inventory. I have 3 items A, B, C. In each sale, a customer can buy all three, just two or one of the items in whatever quantity they wish. On each day I make purchases of varying quantities of A, B & C. I cannot figure out how to use rollup to give me a total of purchases, sales and purchases - sales in my inventory. Images of my three tables below.



Hi @Coco_Custo,

Welcome to Airtable Community !

You cannot use Rollup in your current setup. In order to use Rollup, you need to Link a field first.

So instead of have a field for item A, Field for B, field for C, and so on, you should have 1 field that is Linked to you Inventory Table where you enter the item and the qty, then you can Rollup in Inventory.

BR,
Mo

Thank you for your response. To clarify. I would create a field called product ordered and link it to inventory. And then have another column for quantity? Would this limit my customers order to a single item? So if a customer places an order that includes A & B how could I resolve that?