title: Combine Multiple Column values into one Row
body: <p>I have the data like below where I want to combine the rows having  null values with not null values.</p>
  
  <pre><code>ID    ColA    ColB      ColC     ColD
  1     A1      B1        null     null
  1     A2      B2        null     null
  1     null    B3        C1       D1
  2     A3      B3        null     null
  3     null    null      C3       D3
  </code></pre>
  
  <p>Expected Result:</p>
  
  <pre><code>ID  ColA   ColB    ColC     ColD
  1   A1      B1     C1       D1
  1   A2      B2     C1       D1
  2   A3      B3     null     null
  3   null    null   C3       D3
  </code></pre>
  
  <p>Basically for a single ID multiple rows (different COLA)can exist but only one row with null ColA.</p>
  
  <p>ColC and ColD will always be null for the rows having not null ColA.</p>
  
  <p>I want to merge the ColB,ColC and ColD values of the row having null ColA with all the rows having not null ColA.</p>