On 18 May 2013 06:15, Michael Haberler <mai...@mah.priv.at> wrote: > tools(toolid, length, diameter, other-non-offset parameters) > offsets(offsetid, xoffset,yoffset..., purpose) (purpose could be: > coordinate system offset, wear, tool holder..) > > then you have a relation describing the active offsets, which is 1:N in > nature (a tool can have an arbitrary number of offsets or none at all): > > tooloffsets(toolid, offsetid) (only toolid is a primary key)
I think toolid is the wrong primary key there, assuming that primary keys are unique. I think that the "relation" (if I have my technical terms correct) is tooloffsets(tooloffsetid, toolid, offsetid) To take a concrete example, tools 11 and 22 both with offsets 33 and 44 applied would be: tooloffsetid toolid offsetid 1 11 33 2 11 44 3 22 33 4 22 44 -- atp If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto ------------------------------------------------------------------------------ AlienVault Unified Security Management (USM) platform delivers complete security visibility with the essential security capabilities. Easily and efficiently configure, manage, and operate all of your security controls from a single console and one unified framework. Download a free trial. http://p.sf.net/sfu/alienvault_d2d _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
