title: Google Bigquery Legacy SQL - How to return a null or zero if no results returned?
body: <p>Say I had the following table</p>
  
  <pre><code>month    region   revenue   
  ------  -------- ---------- 
   jan     north      100
   feb     north      150
   mar     north      250
  </code></pre>
  
  <p>How would I be able to query the above table to get the following results?:</p>
  
  <pre><code>month    region   revenue   
  ------  -------- ---------- 
   jan     north      100
   feb     north      150
   mar     north      250
   apr     north       0
   may     north       0
   jun     north       0
  </code></pre>
  
  <p>0's can be null's or vice versa. Essentially trying to add empty/null fields into my query (in this case the apr, may, jun rows). Any help would be much appreciated</p>
  
  <p>Thanks</p>