# Inventory Project **URL:** \ **Category:** Rails\ **Created:** [March 15, 2006, 3:38am UTC](https://www.ruby-forum.com/t/inventory-project/82061 "2006-03-15T03:38:11Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![rahul\_m](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/43a26b/32.png) [@rahul\_m](https://www.ruby-forum.com/u/rahul_m)\ **Post date:** [March 15, 2006, 3:38am UTC](https://www.ruby-forum.com/t/inventory-project/82061/1 "2006-03-15T03:38:11Z")
I am trying to write a inventory web application with RoR so that I can keep track of hardware and software purchased by the company. I would also like to be able to associate products we buy with users and departments. I would like it if you could enter in products (since we purchase many of the same) into a product list. Then you could add a user or department and check off which products he has and then maybe some AJAX for cool effects for entering the serial numbers or additional information. I am not sure if it is the best way but I wanted to add a new column to the “users” table everytime a product was entered and then that would be available to select. I would like to know how I would have to have this project designed so that it can work within the MVC framework and what tables you think I might need. ~Rahul ---
**Author:** ![rahul\_m](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/43a26b/32.png) [@rahul\_m](https://www.ruby-forum.com/u/rahul_m)\ **Post date:** [March 15, 2006, 4:30am UTC](https://www.ruby-forum.com/t/inventory-project/82061/2 "2006-03-15T04:30:03Z")
Hi Rahul, > From your description I don’t think that adding a column to the user table > would be wise. This would limit the number of products that you could > add > to what ever the database can handle as the number of fields. Rather if I have understood you correctly you could use a table structure like: Products id name user\_id department\_id … Users id … Departments id … Then your classes could be something along the lines of Product belongs\_to :user belongs\_to :department User has\_many :products Department has\_many :products You could then add products into a list, and associate them with either a department, a user or both. Cheers ---
**Author:** ![rahul\_m](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/43a26b/32.png) [@rahul\_m](https://www.ruby-forum.com/u/rahul_m)\ **Post date:** [March 15, 2006, 4:48am UTC](https://www.ruby-forum.com/t/inventory-project/82061/3 "2006-03-15T04:48:26Z")
On Tue, 2006-03-14 at 20:37 -0600, Rahul M. wrote: > like to know how I would have to have this project designed so that it > can work within the MVC framework and what tables you think I might need. > > ~Rahul Adding columns is not just a bad idea … it is an evil idea that will make the product unusable in the long term. You will need at least these tables: ITEMS: list of available items and generic sorts of information about them ITEM\_ATTRIBUTES: name -\> value attribute pairs for each item USERS: list of users known to the system USER\_ATTRIBUTES: name -\> value attribute pairs for each user DEPARTMENTS: list of departments known to the system INVENTORY: list of all instances of inventory items and where to find them (user, department, installed in machine, etc) INVENTORY\_ATTRIBUTES: name -\> value attribute pairs for each specific instance of a product If you want to track inventory history, which is required in some cases, you may need to be a bit creative around the INVENTORY table. Use the name-attribute pairs unless you find that you are always keying in the same type of information - serial number for example. Rows (data) can be maintained by the users, but columns (metadata) require a programmer’s continual input. Use surrogate keys (means something to the DBMS, but has no business meaning) for robustness and long term maintainability. I hope this helps.