title: Setting Big Query variables like mysql
body: <p>what is the bigquery equivalent to mysql variables like?</p>
  
  <pre><code>SET @fromdate = '2014-01-01 00:00:00',  -- dates for after 2013
  @todate='2015-01-01 00:00:00',
  
  @bfromdate = '2005-01-01 00:00:00', -- dates for before 2013
  @btodate = '2005-01-01 00:00:00',
  
  @achfromdate  = '2013-01-01 00:00:00', -- dates for ACH without submit time in 2013
  @achtodate  = '2013-01-01 00:00:00',
  
  @currency="USD";
  </code></pre>