SQL可以跨多个表计算聚合函数吗？
发布时间：2020-12-12 06:53:57 所属栏目：MsSql教程 来源：网络整理
导读：假设我有两个现有的桌子,“狗”和“猫”： dog_name | owner ---------+------ Sparky | Bob Rover | Bob Snoopy | Chuck Odie | Jon cat_name | owner ---------+------ Garfield | Jon Muffy | Sam Stupid | Bob 如何使用此输出编写查询？ owner | num_dogs
假设我有两个现有的桌子,“狗”和“猫”：
dog_name | owner ---------+------ Sparky | Bob Rover | Bob Snoopy | Chuck Odie | Jon cat_name | owner ---------+------ Garfield | Jon Muffy | Sam Stupid | Bob 如何使用此输出编写查询？ owner | num_dogs | num_cats ------+----------+--------- Bob | 2 | 1 Chuck | 1 | 0 Sam | 0 | 1 Jon | 1 | 1 解决方法select owner,sum(num_dogs),sum(num_cats) from (select owner,1 as num_dogs,0 as num_cats from dogs union select owner,0 as num_dogs,1 as num_cats from cats) group by owner （编辑：李大同） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |