title: Is it necessary to explicitly define individual indices/keys on each column in a multi-column primary key?
body: <p>If I have the following MySQL table:</p>
  
  <pre><code>CREATE TABLE IF NOT EXISTS `MyTable` (
    `Date` date NOT NULL DEFAULT CURDATE(),
    `RecordNum` varchar(50) NOT NULL,
    PRIMARY KEY (`Date`, `RecordNum`)
  );
  </code></pre>
  
  <p>...do I have to set up an <code>index/key</code> on Date in order to optimize a query like <code>select RecordNum from MyTable where Date = ?</code> ?  </p>
  
  <p>Does the primary key combo automatically create two separate indices for each column in addition to the combination of them, or do I have to do that myself explicitly?  </p>