Hi @Bill_McIntyre, in order to use the similar to JOINS, you have to link in the main table you are going to select to the other table, using the ‘Link to another record’ column, once you added and linked the record to the main table, you can filter it using the PRIMARY COLUMN column in the other table.
Exp:
‘Main table’, has a link to record column named as ‘Product’, the table ‘Product’, has the primary column as ‘Composed Product Name’, to make it unique, or use and AI column. So, that said, you can select from the table passing the filterByFormula values, something like this:
//in this case i'm using async/await, which doesn't require .then or done
try{
let records = await base('Main table').select({filterByFormula: "{Product} = \\"Myprimarykeyhere\\""}).all();
} catch (err) { console.error(err); }
Then you can catch only the row you want, referencing it by “foreign key”. There are other formulas to use if you need and AND, OR, etc. See: https://support.airtable.com/hc/en-us/articles/203255215-Formula-field-reference