数据库学习（四）with as （补充 nvl 和 count 函数）

时间：2019-01-03 19:28:19 阅读：189 评论：0 收藏：0 [点我收藏+]

　　with as 的专业解释我这就不详细说明了，我这就梳理下我自己的实践应用，就是根据某个条件查询出结果集放在一个临时表里面，可以创建多个临时表，然后再从这些临时表中查询出要的数据。

　　参考资料：https://www.cnblogs.com/Niko12230/p/5945133.html

　　　　　　 http://www.cnblogs.com/CareySon/archive/2011/12/12/2284740.html

查询语句：

--开店数
WITH temp_reg AS
          (SELECT a.app_muid
                 ,a.user_id
                 ,a.created_time
           FROM   dataayn_v1.dci_user_action_register a
                  inner join dataayn_v1.dci_stores b on a.user_id  = b.user_id
           WHERE  b.open_time < to_date(‘2018-10-01‘,‘yyyy-mm-dd‘)
                  AND b.open_time >= to_date(‘2018-09-01‘,‘yyyy-mm-dd‘)),
         temp_mapp AS
          (SELECT b.app_muid
                 ,b.hannels
                 ,b.advertiser_id
           FROM   dataayn_v1.dci_appmuid_hannels_mapp b
           WHERE  b.created_time = (SELECT MIN(created_time)
                                    FROM   dataayn_v1.dci_appmuid_hannels_mapp d
                                    WHERE  d.app_muid = b.app_muid))
                                    
         SELECT b.hannels
               ,b.advertiser_id
               ,nvl(COUNT(1),0) 开店数
         FROM   temp_reg a
         INNER  JOIN temp_mapp b
         ON     a.app_muid = b.app_muid
         GROUP  BY b.hannels
                  ,b.advertiser_id ;