Question

Here’s a Item table that stores basic item information like name, price, color etc.

Now, I need to keep track of materials used in an item like say, cotton, gems, rhinestone, leather etc. One required feature is to identify the items that is made of one or more partiuclar materials. For example, given the materials cotton and rhinestone, I should be able to output a list of all the items that is made of cotton and rhinestone (among other possible materials).

So, what’s the best way to design the tables for this particular requirement taking performance into account?

Answer 1

You should have a table for item and one for material, and then use a junction table to define which items contain which materials and vice-versa.. Something like this would be best:

Item

Id
Name
Price
colour

Material

Id
Name
Description
...

Item_Material

Item_Id (FK to Item.Id)
Material_Id (FX to Material.Id)

Then, if you want to get all the items with cotton in them, you’d write a query like:

SELECT ITEM.*
FROM ITEM INNER JOIN ITEM_MATERIAL ON ITEM.ID = ITEM_MATERIAL.ITEM_ID
INNER JOIN MATERIAL ON MATERIAL.ID = ITEM_MATERIAL.MATERIAL_ID
WHERE MATERIAL.NAME = 'cotton'

Or for all materials making up an item:

SELECT MATERIAL.*
FROM ITEM INNER JOIN ITEM_MATERIAL ON ITEM.ID = ITEM_MATERIAL.ITEM_ID
INNER JOIN MATERIAL ON MATERIAL.ID = ITEM_MATERIAL.MATERIAL_ID
WHERE ITEM.NAME = 'handbag'