Connect 2 Records from 2 Tables, based on 2 or More Parameters

Hi I'm sorry, I was making this post in a hurry. Let me explain this:

So, we have 2 tables - Raw Shipment ID and Raw PI ID. We work with both our distributor side and supplier side, that's why we have 2 tables PI- being the orders on our supplier side, and Shipments on our distributor side.

We can't restructure or combine these two tables as different teams (which work independently) work on each table, so restructuring them would burn more time than we can save.

Now, for the 'Raw PI ID' table, we have a "PI" and the product ID represented by the column "SKU".

For the Shipment ID table, each shipment line item still has a "PI" column (but since the PI can be split into multiple shipments, the PI can change in nomenclature, ie. PI 1 from the table 'Raw PI ID' can be split into USA and Canada shipments, which when translated on the 'Shipment ID' table becomes, PI 1 USA and PI 1 CA). Also it has an SKU field.

These PI orders can be split into multiple shipment IDs. Essentially, it's a 1:N, Raw PI ID : Raw Shipment ID table relationship. 

My current solution:

-Firstly, since the "PI" on the shipment table can be added with other characters (PI USA, PI CA, etc), it can just be remedied by slicing the PI data into different arrays through their spaces, and then extracting the first word on the array, which would be the root PI ID.

-Next, since I don't want to deal with "and" qualifiers, and since the SKU-PI ID is unique, I can just concatenate both columns into a single array, thereby producing a unique SKU-PI column, reducing the parameter to match into 1 instead of 2. I named this "SKU-PI ID" pairing column into "LINK" (from the Shipments table) and "LINK 2" (from the PI ID table). 

-I then created a button trigger (on the shipments table) that when pressed will link the item from the matching records from the shipments table to the PI ID table when clicked. Again, this button is on the shipments table:

let x := this.LINK;
let y := last((select 'Raw PI ID' where 'LINKER 2' = x).Id);
'Raw PI ID' := y

Here's what I want to ask help for:

Suppose we have 1,000 new records uploaded by CSV, it would be logistically impossible to religiously click the button for each of the 1,000 new records.

Is there a way to make a button that initiates a loop that matches the record from the Raw Shipment ID table to the RAW PI ID table, given LINKER as the concatenated column for the SKU and PI Id?

Thanks!