MySQL DISTINCT

DISTINCT（COL）用来对结果去除重复

比如表内容如下：

SELECT DISTINCT(id)FROM yww_test

下面的例子实现：选择过去一天，没有出现过的数据

-- 统计最原始的未上线采集数据，准备和其他表合并DROP VIEW if EXISTS `unconnected_elemeterhead`;CREATE VIEW unconnected_elemeterheadASSELECTDATE_SUB(curdate() , INTERVAL 1 DAY) as 'uhead_date',   head.`NAME` as 'uhead_name',head.PADDRESS as head_address,head.E_BUREAU_ID as bureau_id,head.ID as 'uhead_id'FROMe_elemeterhead_link39 AS headWHEREhead.`STATUS` = 0AND head.ID NOT IN (SELECT DISTINCT(a.E_ELEMETERHEAD_ID)FROMe_eledata AS aWHEREto_days(now()) - to_days(a.DLDT) = 1);

注意：如何确定昨天，如何统计未出现的ID