问题
I currently have a table that stores the materials used to create an item
Item (material1, material2, material3)
Another material has recently been added. However, I want to normalize this table so that in the future, adding a new material won't need a new column to be added to the database. I extracted the materials into the following junction table
ItemJuncMaterial (id, itemId, materialid)
However, the catch is that the order of the materials matter. So this junction table won't allow me to run this query based on materials to get the item
select itemid from ItemJunMaterial where materialid in (1,2,3)
This can return items that use 2,3,1 or could even use two materials 1,2. Is there a better way to split up this table to normalize it and make it more dynamic?
回答1:
You should consider a "bill of materials" (BOM) pattern (see here or here). The intersection of a BOM can include extra information about the composition, such as quantity of each component. You could easily include the sequence or priority of the component in that intersection just as easily.
来源：https://stackoverflow.com/questions/39416557/normalize-a-table-with-tightly-coupled-data