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POWhat's the best way to handle one-to-one relationships in SQL?
 

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    <p>Let's say I've got Alpha things that may or may not <em>be</em> or be <em>related to</em> Bravo or Charlie things.</p> <p>These are one-to-one relationships: No Alpha will relate to more than one Bravo. And no Bravo will relate to more than one Alpha.</p> <p>I've got a few goals:</p> <ul> <li>a system that's easy to learn and maintain.</li> <li>data integrity enforced within my database.</li> <li>a schema that matches the real-world, logical organization of my data.</li> <li>classes/objects within my programming that map well to database tables (à la Linq to SQL)</li> <li>speedy read and write operations</li> <li>effective use of space (few null fields)</li> </ul> <p>I've got three ideas&hellip;</p> <pre><code>PK = primary key FK = foreign key NU = nullable </code></pre> <p>One table with many nullalbe fields (flat file)&hellip;</p> <pre><code> Alphas -------- PK AlphaId AlphaOne AlphaTwo AlphaThree NU BravoOne NU BravoTwo NU BravoThree NU CharlieOne NU CharlieTwo NU CharlieThree </code></pre> <p>Many tables with zero nullalbe fields&hellip;</p> <pre><code> Alphas -------- PK AlphaId AlphaOne AlphaTwo AlphaThree Bravos -------- FK PK AlphaId BravoOne BravoTwo BravoThree Charlies -------- FK PK AlphaId CharlieOne CharlieTwo CharlieThree </code></pre> <p>Best (or worst) of both: Lots of nullalbe foreign keys to many tables&hellip;</p> <pre><code> Alphas -------- PK AlphaId AlphaOne AlphaTwo AlphaThree NU FK BravoId NU FK CharlieId Bravos -------- PK BravoId BravoOne BravoTwo BravoThree Charlies -------- PK CharlieId CharlieOne CharlieTwo CharlieThree </code></pre> <p>What if an Alpha must be either Bravo or Charlie, but not both?</p> <p>What if instead of just Bravos and Charlies, Alphas could also be any of Deltas, Echos, Foxtrots, or Golfs, etc&hellip;?</p> <hr> <p><strong>EDIT:</strong> This is a portion of the question: <a href="https://stackoverflow.com/questions/56981/which-is-the-best-database-schema-for-my-navigation#57056">Which is the best database schema for my navigation?</a></p>
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