Question

我想计算一个分组之后的特定列，但结果与我的预期不同。情况就是这样：假设我有一张包含这些数据的表格：

sdate           name    collected
2017-01-01      John    5
2017-01-01      John    3
2017-01-01      Wick    6
2017-01-01      Wick    6
2017-01-02      Mary    5
2017-01-02      Pete    1
2017-01-02      Mary    4
2017-01-02      Pete    2
2017-01-03      John    8

我希望使用以下查询获得collected的总和：

select name, sdate, sum(collected) as count from test 
group by name, sdate 
order by sdate

输出：

sdate           name    count 
2017-01-01      wick    9
2017-01-01      john    11
2017-01-02      pete    3
2017-01-02      mary    9
2017-01-03      john    8

问题：我想从上面的结果中select count(name) group by sdate，结果将是：

sdate           name    count    countName
2017-01-01      wick    9        2
2017-01-01      john    11       2
2017-01-02      pete    3        2
2017-01-02      mary    9        2
2017-01-03      john    8        1

如何实现这一目标？我试着用下面的声明做这件事：

select A.*, count(A.name) as countName
from 
(select sdate, name, sum(collected) as count from test 
group by name, sdate 
order by sdate) A
group by A.sdate

输出：

sdate       name    count   countName
2017-01-01  wick    9       2
2017-01-02  mary    9       2
2017-01-03  john    8       1

计数是正确的，但行数将被分组，这是我不想要的。知道如何在不删除行的情况下实现它吗？

Answer 1

目前还不是很清楚你想要什么，但似乎你想知道每组中有多少行。将count(*) as countName添加到原始查询中：

select name, sdate, sum(collected) as count, count(*) as countName
from test
group by name, sdate 
order by sdate

Answer 2

试试这个：

select name, sdate, sum(collected) as count, count(*) as countName
from test 
group by name, sdate 
order by sdate;

MySQL按分组计算特定列

2 个答案: