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POHibernate: table per concrete class vs. table per subclass
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  1. POHibernate: table per concrete class vs. table per subclass
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    copied!<p>I'm planing / designing my database for my current project (Java). For this project I'm going to use hibernate.</p> <p>In my project I have a base class/interface called Command. In fact the Command class contains only a field id (unique).</p> <pre><code>public interface Command { public int getId(); public void execute(); } </code></pre> <p>So what every subclass of Command has in common is an unique id and a method called execute, which is implemented by the subclasses.</p> <p>There exists many sub classes like MoveCommand, ResizeCommand etc. which has no common data fields (except the id).</p> <p>For example:</p> <pre><code>public class MoveCommand implements Command { private int id; private int oldX; private int oldY; private int newX; private int newY; public void execute() { ... } public int getId(){return id; } } public class ResizeCommand implements Command { private int id; private int oldWidth; private int oldHeight; private int newWidth; private int newHeight; public int getId(){return id; } public void execute() { ... } } </code></pre> <p>Then I have another class called Document, which contains a list of commands</p> <pre><code>public class Document { private List&lt;Command&gt; commands; } </code></pre> <p>So a lot of queries of the base class "select from Command" were executed on runtime.</p> <p>My question is: What kind of inheritance strategy should I use in this case to get the best performance.</p> <p>In SQL: does JOIN (table per subclass ) or UNION (table per concrete class) perform better in this case?</p> <p>Does anyone has experience with this topic?</p> <p>I guess table per subclass would be the better (design) solution, but I'm not sure about it, since there would exist a database table with a single column (id), because that's the only thing that commands have in common. </p>
 

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