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copied!<p>Sorry it's taken so long to come back to you. What you are asking is not specific to Objective-C. My first introduction of connecting Object-oriented code to RDBMS was Enterprise Object Frameworks in NextStep. But since then, that idea has been copied in most object-oriented languages including Java and Ruby (see ActiveRecord).</p> <p>Conceptually, on the programming side there is usually a entity class that is used to represent each row of a table. In some cases, such as CoreData or WebObjects, a map is used to create an interface between the application code and the database. Because of this map, a developer can use instances of the generic entity class to represent the data. Of course, many times that class is subclassed to added methods specific to a particular entity.</p> <p>For example, say you have a table for contacts, which has a column for first name and a column for last name. Often in an application you want to display the full name. In a subclass of the entity class, one can add a method that returns the first and last name as a single string.</p> <p>In other frameworks, such as ActiveRecord, I believe you must always have a subclass that represents each table.</p> <p>Conceptually, I find Object-Oriented programming to align well with RDBMS.</p> <p>Table (contacts) -> Class (Contact)</p> <p>Row -> Instance of class (aContact)</p> <p>Columns (firstName) -> Properties (aka instance variables, attributes) (firstName)</p> <p>Relationships:</p> <pre><code>to-one (father) -> Properties (father, an instance of Contact) to-many (emailAddresses) -> Array (emailAddresses, an array of instances of EmailAddress class) </code></pre> <p>Hope this answers your question better,</p>

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