title: How to get the first not null value from a column of values in Big Query?
body: <p>I am trying to extract the first not null value from a column of values based on timestamp. Can somebody share your thoughts on this. Thank you.</p>
  
  <p>What have i tried so far?</p>
  
  <pre><code>FIRST_VALUE( column ) OVER ( PARTITION BY id ORDER BY timestamp) 
  </code></pre>
  
  <p><strong><code>Input :-</code></strong></p>
  
  <pre><code>id,column,timestamp
  1,NULL,10:30 am
  1,NULL,10:31 am
  1,'xyz',10:32 am
  1,'def',10:33 am
  2,NULL,11:30 am
  2,'abc',11:31 am
  
  Output(expected) :-
  1,'xyz',10:30 am
  1,'xyz',10:31 am
  1,'xyz',10:32 am
  1,'xyz',10:33 am
  2,'abc',11:30 am
  2,'abc',11:31 am
  </code></pre>