Question

我正在使用VBA使用ADO构建SQL查询。我有一个连接查询，如下所示：

select user.id,user.city,action.id
from user
left join
action
on
user.id=action.userID

我想添加一个给我user.city计数的列，以便我的结果看起来像：

+---------+-----------+-----------+-----------+
| user.id | user.city | cityCount | action.id |
+---------+-----------+-----------+-----------+
|       1 | DMZ       |         3 |         9 |
|       1 | DMZ       |         3 |        44 |
|       2 | KLF       |         1 |     23523 |
|       3 | DMZ       |         3 |         3 |
+---------+-----------+-----------+-----------+

我想也许我必须收集此查询的汇总并将其加入原始查询中，如下所示：

select user.id,user.city,cc.cityCount,action.id,action.action
from user
left join
action
on
user.id=action.userID
left join
(select city,count(city) as cityCount from 
 (select user.id,user.city,action.id,action.action
  from user
  left join
  action
  on
  user.id=action.userID) 
 group by city) cc
on
user.city=cc.city

是否有更直接的方法来获得此计数而无需两次写出（并执行）相同的查询？

Answer 1

另一种方法是使用相关子查询：

select u.id, u.city, a.id,
       (select count(*)
        from user u2 join
             action a2
             on u2.id = a2.id
        where u2.city = u.city
       ) as cityCount
from user u left join
     action a
     on u.id = a.userID;

如何在连接结果中包含计数？

1 个答案: