title: Convert table column data type from blob to raw
body: <p>I have a table designed like,</p>
  
  <pre><code>create table tbl ( 
    id number(5),
    data blob
  );
  </code></pre>
  
  <p>Its found that the column <code>data</code> have 
  very small size data, which can be stored in <code>raw(200)</code>:</p>
  
  <p>so the new table would be,</p>
  
  <pre><code>create table tbl ( 
    id number(5),
    data raw(200)
  );
  </code></pre>
  
  <p>How can I migrate this table to new design <strong><em>without loosing the data in it</em></strong>.</p>