layout question

Hi list,

I must build a kind of ERP and I wonder what's the best DB layout,
especially about quotations/orders/delivery orders/invoices/RMAs/credit
notes.

It must be very scalable (say from 10 invoice a day to 2,000 or even more.)

As these docs' structures are very close, what is the best:
to have one table per kind of doc and to copy info from one to another,
or to have only one table with a flag telling the doc's type and external
sequences to keep numbering coherent? (also means the docs' lines table
will be pretty huge.)

JY
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