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copied!<p>I've done something like this for publisher trying to attach repair procedures to a product. The product is identified by a four-part primary key: Year, Make, Model, Engine, or YMME, and the vehicles table looked like this (simplified):</p> <pre><code>VEHICLES year integer make varchar model varchar engine varchar </code></pre> <p>The PARTS table has to be linked to an entity in the VEHICLES table. A part might work with a specific year and make and model, but not when a specific engine was installed.</p> <p>In your case, you have to decide what constellation of attributes uniquely identifies a bicycle. If you're tracking bikes from multiple makers, you need MAKE. If things change from year to year, you need YEAR. If there is a difference from model to model, you need MODEL. If, say, a part will work if the frame is aluminum but not if the frame is steel, you'd need FRAME_MATERIAL or FRAME_GAUGE as well, in place of ENGINE, or you'd need a separate model one for aluminum, the other for steel.</p> <pre><code>VEHICLES year make model frame </code></pre> <p>Then you could simply have an intermediary table:</p> <pre><code>VEHICLE_PARTS partid integer foreign key references PARTS year make model frame ... </code></pre> <p>or</p> <pre><code>VEHICLE_PARTS partid integer foreign key references PARTS year make model (frame material is handled by a separate model) </code></pre> <p>Your structure has to answer the question: Will this part work with <em>that</em> bike? The mere presence of the partid in the VEHICLE_PARTS table should imply, Yes it does. You really want to avoid having an Exceptions field in the VEHICLE_PARTS table where there is some human-readable notation that says the part is incompatible with the bike in question when rams-horn handlebars are used. You should really create a separate model to handle things like that.</p>

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