Help with a DB design II
Posted by: Rui Silva
Date: March 24, 2011 05:41AM

Hello I need help whit the following question.
Lest say I have a material which is made of either an alloy or an element (a medal can be made of silver (element) or bronze (alloy of 12%tin and 88%cupper (elements)).
A material also can be made of a combination of cupper (element) and still (alloy of 2 elements) and for discrimination purpose cannot be an alloy of 3 elements.
So far I have the following:
metal_alloy
#ID_METAL_ALLOY
NAME

metal_alloy_composition
#ID_CHEMICAL_ELEMENT - FK
#ID_METAL_ALLOY - FK
PART


chemical_element
#ID_CHEMICAL_ELEMENT
NAME
CHEMISTRY_SYMBOL

material_composition
#ID_MATERIAL - FK
#ID_CHEMICAL_ELEMENT - FK
#ID_METAL_ALLOY - FK

material
#ID_MATERIAL
NAME

But I’ve a feeling that something is not right....

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Help with a DB design II
March 24, 2011 05:41AM


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