title: mysql concat from select result
body: <p>I would like to insert data in MySQL with automatic naming on field <code>username</code> but how i can do it?.
  <br/>
  Currently data at table is:</p>
  
  <pre>
  +----+----------+
  | id | username |
  +----+----------+
  |  1 | admin1   |
  |  2 | admin2   |
  +----+----------+
  </pre>
  
  <p>I try using this sql but it's can't: 
  <br/></p>
  
  <pre>
  INSERT INTO `tbl_user` (
  `username`
  )
  VALUES (
  CONCAT('admin',(SELECT MAX(SUBSTRING_INDEX(`username`,'admin',-1))+1 FROM `tbl_user`))
  );
  </pre>
  
  <p>and get error message <code>#1093 - You can't specify target table 'tbl_user' for update in FROM clause</code><br/><br/>
  Final result i want is:</p>
  
  <pre>
  +----+----------+
  | id | username |
  +----+----------+
  |  1 | admin1   |
  |  2 | admin2   |
  |  6 | admin3   |
  |  9 | admin4   |
  +----+----------+
  </pre>
  
  <p>is that possible? thanks.</p>