title: oracle decode group by warning
body: <p>I have this code </p>
  
  <pre><code>for x_eo in ( select decode(mod(card_name_id,2),0,1,1,2) e_o, count(*) nr 
                          from  rp_Deck where session_id=p_session_id_in 
                         and position&lt;=35 group by mod(card_name_id,2) )
  </code></pre>
  
  <p>I am getting sqldeveloper warning that select list inconsistent with group by.
  And developer gives me solution:</p>
  
  <pre><code>select decode(mod(card_name_id,2),0,1,1,2) e_o, count(*) nr 
                          from  rp_Deck where session_id=p_session_id_in 
                         and position&lt;=35 group by mod(card_name_id,2), card_name_id, 2, decode(mod(card_name_id,2),0,1,1,2) )
  </code></pre>
  
  <p>What is difference between these two group by ?
  Thanks !</p>