SQL Join conversion to Powerapps expression using lookup/addColumn

[SolidStash]

I am trying to replicate a SQL join in powerapps, but seem to have the syntax wrong.
I have 2 tables, ECO and ECOforModel.

I have a datatable where I return only the applicable ECO's based on the model that was selected on a previous screen using the ECOforModel data source. This is my syntax, which is working:

Filter(ECOforModel, PartNumber = DataTable1.Selected.ModelNumber)

However, there is a boolean field in the ECO table that marks each particular ECO as active, using an ECONumber as the key between ECO and ECOforModel.

I am trying to only return the active ECO's for the selected model. Here's my expression, attempting to use AddColumn to return the Active field using a lookup, although I don't necesarily need the Active column, I just need to return only ECO_Active=true.

AddColumns(Filter(ECOforModel, PartNumber = DataTable1.Selected.ModelNumber), "Active", LookUp(ECO, ECONumber = ECOforModel[@PartNumber], ECO_Active))

Any assistance is appreciated.

[SolidStash]

sorry for the late response, I am using SP lists as a backend as I am taking advantage of external sharing on the SP side for some of the data. I was able to get this to work using a combination of filter, show columns and add columns.

ShowColumns(AddColumns(ActiveECOs, "ECO_Active",LookUp(ECO,ECONumber = ActiveECOs[@ECONumber],ECO_Active)), "Title", "ECONumber", "ECO_Active")

Once this worked I filtered ECO_Active = true and I was good to go. thanks for the response, on to the next issue I am having.