title: Using a DATE field as primary key of a date dimension with MySQL
body: <p>I want to handle a date dimension in a MySQL datawarehouse. (I m a  newbie in the DW world)</p>
  
  <p>I made some searches with google and saw a lot of table structures (most of) date dimension where the Primary Key is a simple <code>UNSIGNED INTEGER</code>.</p>
  
  <p>Why don't use a <code>DATE</code> field as primary key since with MySQL it is 3 Bytes VS 4 Bytes for <code>INTEGER</code>?</p>
  
  <p>Ex:</p>
  
  <pre><code>CREATE TABLE dimDate
  id INTEGER UNSIGNED NOT NULL PRIMARY AUTOI_NCREMENT,
  date DATE NOT NULL,
  dayOfWeek
  ...
  </code></pre>
  
  <p>VS</p>
  
  <pre><code>CREATE TABLE dimDate
  date DATE NOT NULL PRIMARY,
  dayOfWeek
  ...
  </code></pre>