title: SQL - Find all possible combination
body: <p>I need help finding all possible combination of value in database, for Example i have this table:</p>
  
  <pre><code>ITEM_SET           Support  
  I1               0.244999999
  I2               0.274999999     
  I3               0.258333333    
  I4               0.103333333  
  </code></pre>
  
  <p>i need to find all possible combination like this :</p>
  
  <pre><code>I1,I2    I1,I2,I3    I1,I2,I3,I4
  I1,I3    I1,I2,I4
  I1,I4    I1,I3,I4
  I2,I3    I2,I3,I4
  I2,I4 
  I3,I4
  </code></pre>
  
  <p>*Please note that this formatting meant only to help reading, as what i need is only a list of the possible combination like this Table:</p>
  
  <pre><code>ITEMSET
  I1               
  I2                    
  I3                 
  I4  
  I1,I2    
  I1,I3    
  I1,I4    
  I2,I3    
  I2,I4 
  I3,I4
  I1,I2,I3 
  I1,I2,I4 
  I1,I3,I4 
  I2,I3,I4   
  I1,I2,I3,I4
  </code></pre>