This article outlines the database structure for the MMv4 product_stock_assoc database table.

• pid
  Reference to the product's SID number: product.id.
  int(10) | unsigned | indexed
• stock_id
  Reference to the stock object's SID number: stock_level.id.
  int(10) | unsigned | indexed
• units_per_qty
  For every one unit purchased by the customer, the stock level will be reduced by this number.
  int(10) | unsigned