title: How to set mysql Default value NONE
body: <p>I am using a table  "media_content" which has columns</p>
  
  <pre><code>id varchar(50) NOT NULL,
  shorttitle varchar(200) DEFAULT NULL,
  sourceimage blob
  </code></pre>
  
  <p>Later i modified the sourceimage column to  default values as <code>NULL</code></p>
  
  <pre><code>ALTER TABLE media_content
  MODIFY COLUMN sourceimage VARCHAR(250) DEFAULT NULL;
  </code></pre>
  
  <p>Now i want to make the <code>sourceimage</code> column default as <code>NONE</code>,  is it possible to do that?</p>