Doctor Orange

I am about to start work on a PHP MySQL project, and I want to get it right from the start to save trouble and threads later ;0) It's a system to track production of, lets say, A CANDY FACTORY! One ORDER has many ITEMS. One ITEM has many UNITS. eg. ORDER #145: 10kg gummi bears 5 complete 5 remaining 12L chocolate-milk 1 complete 2 complete 2 progress 7 remaining The ORDER having two ITEMS; the two ITEMS, (10kg gummi, 12L milk); and each of those ITEMS has been (at some point) broken down into UNITS to be completed. My question is, how do I relate the ORDERS, ITEMS & UNTIS tables? I could have: ORDERS order_id ITEMS item_id order_id* UNITS unit_id item_id* (where every child entry references it's parent entry) Or I could use: ORDERS order_id [b]items[/b](array) ITEMS item_id [b]units[/b](array) UNITS unit_id (where every parent entry references all it's children in an array) ___________________________________________________________ I am new to MySQL (in fact, all databases) so I'm still learning the correct, efficient and easy way to do these things. What do you suggest? Thanks so much :0)