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    <p>1NF bans repeating lists in a row. Your design violates this, and so would the following design:</p> <pre><code>Student Phones 'John D' '555-5555, 666-6666, 777-7777' 'Sally S' '111-1111, 222-2222' </code></pre> <p>The following design would violate 2NF, because the only primary key is <code>Name, Phone</code>, but the <code>Address</code> attribute does not depend on the <code>Phone</code>:</p> <pre><code>Name Phone Address 'John D' '555-5555' '1 Square Village' 'John D' '666-6666' '1 Square Village' 'John D' '777-7777' '1 Square Village' 'Sally S' '111-1111' '999 Flash City' 'Sally S' '222-2222' '999 Flash City' </code></pre> <p>The next design would violate 3NF, because AreaName does not depend on Name, but only on Area:</p> <pre><code>Name Area Phone AreaName 'John D' '555' '5555' '111name' 'John D' '666' '6666' '666name' 'John D' '777' '7777' '777name' 'Sally S' '111' '1111' '111name' 'Sally S' '222' '2222' '222name' </code></pre> <p>Even if your design violates 1NF, it's an excellent choice. The complexity of adding a <code>PhoneNumber</code> table is hardly ever justified. </p> <p>Think about how hard an update to a customer becomes if you conform to 1NF. The numbers would be in a separate table. So if someone submits a form with an updated list of phone numbers, how would you change the database? First you'd have to retrieve the existing list of numbers. Then you'd have to compare them to the submitted list. Then you'd have to delete or insert rows based on the difference. One heck of a complex solution.</p> <p>If you stick to your solution, you can just update the three columns. The saved time can be spend on real features! Or even writing long answers on Stack Overflow.</p>
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    1. POIs this a 1NF failure?
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    1. COlol. So it seems that a 1NF failure can occur even if there is a limit on the number of repeating groups, not just for repeating groups for where there is no set limit.
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    2. COActually, you'd just delete all his phone numbers and then insert all from the form - or you'd just make a separate form (ajax makes this nice) where you could delete single phone numbers and add new ones. So all in all it highly depends on your application what's more comfortable. Of course only unless you use an ORM where the separate table with proper relationships would give you an array for the user's phone numbers.
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    3. COCorrect. Normal forms come from "Relational Algebra", for a good introduction see the [Stanford free class](http://www.db-class.org/). I would say that normal form is a great tool, but you have to weigh the cost and benefit, and not apply it blindly.
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