title: Liquibase Add default value
body: <p>I have created a table with name person and added a column 'phone_number' using liquibase changeset. But now I want to add a default value for it. but it did not work, so far I have tried this: 
  </p>
  
  <pre><code>&lt;addDefaultValue columnName="phone_number"
                   defaultValue="+923331234567"
                   tableName="person"/&gt;
  </code></pre>
  
  <p></p>
  
  <p>and</p>
  
  <pre><code>&lt;changeSet author="haseeb" id="20160413123500"&gt;
      &lt;update tableName="person"&gt;
          &lt;column name="phone_number" type="varchar(255)" defaultValue="+923331234567"/&gt;
      &lt;/update&gt;
  &lt;/changeSet&gt;
  </code></pre>
  
  <p>and</p>
  
  <pre><code>&lt;changeSet author="haseeb" id="20160413123501"&gt;
      &lt;update tableName="person"&gt;
          &lt;column name="phone_number" type="varchar(255)" value="+923331234567"/&gt;
  &lt;/update&gt;
  </code></pre>
  
  <p></p>
  
  <p>Can anyone point out where I did wrong and also would adding default value  will add value to previously added rows?</p>