排序用group by
去除重复用max(expr)
SELECT ed.ID,ed.`NAME`,ed.RATIO,max(e.DLDT),e.TAE,e.TAE/ed.RATIO from e_eledata e , e_elemeterhead ed where e.E_ELEMETERHEAD_ID = ed.ID and ed.`STATUS` = '0' group by ed.ID,ed.`NAME`,ed.RATIO ;
原文：http://blog.csdn.net/calmreason/article/details/40980309