Question

Basically I have a small ‘invoicing’ type system where I have a MySQL table set up for the individual invoices, the invoice lines, and items associated with each invoice, sort of like this:

table invoices:

fields: invoice_id | type | fees | comments | company

—

table invoice_lines:

fields: id | invoice_id | name | description | quantity

—

table invoice_affected_items

fields: id | invoice_id | item_id

I can have many invoice lines and many affected items to one invoice id. In this case would a join be best or should I just join the invoice lines to the table and retrieve the affected items using a separate query?

Thanks.

Answer 1

You could join, but that would result in pulling a lot of extra data. If you join the lines on to the invoices for example, you’d be pulling the invoice multiple times – once for each line…

So to answer your question. I’d do it in separate queries.