Automatically update product quatities from a spreadsheet or flat file

[DrByte]

I'm looking for a way to automatically load / update data from a flat file into the products table. if the entry already exists then I want the product count to be updated

Is there something part of ZEN cart that can already do this?

Not built-in, no. But you could try the Easy Populate addon in the Downloads area.

if not is there a clear explanation of the Database strucutre? like an ERD diagram or something?

The schema is documented here, with links to ERD diagrams near the top of the list: http://www.zen-cart.com/wiki/index.p...atabase_Schema