title: percentile_disc vs percentile_cont
body: <p>What is difference between <code>PERCENTILE_DISC</code> and <code>PERCENTILE_CONT</code>,</p>
  
  <p>I have a table ### select * from childstat</p>
  
  <pre><code>FIRSTNAME                                          GENDER BIRTHDATE     HEIGHT     WEIGHT
  -------------------------------------------------- ------ --------- ---------- ----------
  lauren                                             f      10-JUN-00         54        876 
  rosemary                                           f      08-MAY-00         35        123 
  Albert                                             m      02-AUG-00         15        923 
  buddy                                              m      02-OCT-00         15        150 
  furkar                                             m      05-JAN-00         76        198 
  simon                                              m      03-JAN-00         87        256 
  tommy                                              m      11-DEC-00         78        167 
  </code></pre>
  
  <p>And I am trying differentiate between those percentile</p>
  
  <pre><code>select firstname,height,
         percentile_cont(.50) within group (order by height) over() as pctcont_50_ht,
         percentile_cont(.72) within group (order by height) over() as pctcont_72_ht,
         percentile_disc(.50) within group (order by height) over () as pctdisc_50_ht,
         percentile_disc(.72) within group (order by height) over () as pctdisc_72_ht
  from childstat order by height
  
  
  FIRSTNAME                                              HEIGHT PCTCONT_50_HT PCTCONT_72_HT PCTDISC_50_HT PCTDISC_72_HT
  -------------------------------------------------- ---------- ------------- ------------- ------------- -------------
  buddy                                                      15            54         76.64            54            78 
  Albert                                                     15            54         76.64            54            78 
  rosemary                                                   35            54         76.64            54            78 
  lauren                                                     54            54         76.64            54            78 
  furkar                                                     76            54         76.64            54            78 
  tommy                                                      78            54         76.64            54            78 
  simon                                                      87            54         76.64            54            78 
  </code></pre>
  
  <p>But still can't understand how this two and what is use of those two functions..</p>