title: Impala - Does impala allow multi GROUP_CONCAT in one query
body: <p>For example, I have a table below</p>
  
  <pre><code>+-----------+-------+------------+
  |        Id |      a|           b|
  +-----------+-------+------------+
  |         1 |     6 |         20 |
  |         1 |     4 |         55 |
  |         1 |     9 |         56 |
  |         1 |     2 |         67 |
  |         1 |     7 |         80 |
  |         1 |     5 |         66 |
  |         1 |     3 |         33 |
  |         1 |     8 |         34 |
  |         1 |     1 |         52 |
  </code></pre>
  
  <p>I want the output would be like below by using Impala</p>
  
  <pre><code>+-----------+-------------------+-----------------------------+
  |        Id |     a             |                           b |
  +-----------+-------------------+-----------------------------+
  |         1 | 6,4,9,2,7,5,3,8,1 | 20,55,56,67,80,66,33,34,52  |
  +-----------+-------------------+-----------------------------+
  </code></pre>
  
  <p>In Impala, I have used </p>
  
  <pre><code>SELECT Id, 
         group_concat(DISTINCT a) AS a, 
         group_concat(DISTINCT b) AS b 
  FROM table GROUP BY Id
  </code></pre>
  
  <p>It will always get Syntax error. Just wondering is that we are not allowed to use multi group_concat for one query in Impala? or not allow to use multi Distinct for one query? </p>