title: Calculate average per row in SQL Server
body: <p>I need to calculate the average per day from 1 st record of year for each row.
  I can do it by iterating in a while loop but am sure that I can achieve this simpler. I woould nee a query to calculate the avgAmount near the Amount field. </p>
  
  <p>The average is simply calculated by summing the amounts and divide by the difference between min and max dates for each row.</p>
  
  <pre><code>create table a
  (
  date  datetime,
  dept varchar(50),
  amount float
  )
  
  insert into a values ('2016-02-07', 'abc', 25)
  insert into a values ('2016-02-27', 'abc', 20)
  insert into a values ('2016-03-09', 'abc', 30)
  insert into a values ('2016-03-28', 'abc', 45)
  insert into a values ('2016-04-07', 'abc', 40)
  insert into a values ('2016-04-30', 'abc', 50)
  insert into a values ('2016-05-07', 'abc', 60)
  insert into a values ('2016-05-27', 'abc', 50)
  insert into a values ('2016-06-30', 'abc', 38)
  insert into a values ('2016-07-17', 'abc', 45)
  insert into a values ('2016-07-30', 'abc', 55)
  insert into a values ('2016-08-07', 'abc', 70)
  </code></pre>
  
  <p><a href="http://sqlfiddle.com/#!3/592a3/7" rel="nofollow">SQLFIDDLE</a></p>
  
  <p>Any help please?</p>