title: MYSQL/Exact Target query does not pass validation
body: <p>Exact Target uses MYSQL, however it prevents me from using SOME commands. either wait, I get this error
  "Cannot perform an aggregate function on an expression containing an aggregate or a subquery." </p>
  
  <pre class="lang-html prettyprint-override"><code>select tm.CustomerID as customerid, tp.Category1 as product_category, (SELECT RIGHT(tod.ProductCode,2)) as size, (SELECT count ((SELECT RIGHT(tod.ProductCode,2)))  as unique_size_purchases FROM ent.customer_product_sizing_profile
   GROUP by customerid)
  from ENT.TAR_POS_CUSTOMER as tm
  LEFT OUTER JOIN ENT.TAR_POS_ORDER_HEADER as th
  ON tm.CustomerID=th.CustomerID
  LEFT OUTER JOIN ENT.TAR_POS_ORDER_DETAILS as tod
  ON tod.OrderNumber=th.OrderNumber
  LEFT OUTER JOIN ENT.TAR_POS_PRODUCT as tp
  ON tp.ProductCode=tod.ProductCode
  </code></pre>