使用 group by 计算 sql

Question

我有 table temp 其中包含 4 列作为

create table Temp
(
seqno int identity (1,1),
name varchar(20),
towncd numeric,
Counttown_cd,

)

我想写查询 return 镇的计数，但如果名称和 towncd 相同然后计算在先前记录中添加的裹尸布喜欢

1 man   0001 
2 man   0001 
3 test  0003 
4 man   0001  
5 man   0001

应该return 作为

    1 man  0001 2
    2 man  0001 null
    3 test 0003 1
    4 man  0001 2
    5 man  0001 null

我尝试了以下查询：

    SELECT p.seqno ,p.name,P.towncd ,COUNT(P.towncd )Counttown_cd
                FROM temp P
                GROUP BY P.name,P.towncd ,p.seqno 
                order by p.seqno

Answer 1

您对问题的修改为原始问题添加了空白和孤岛问题。这可以通过子查询中的两个 row_number() 来解决，如下所示：

select seqno, name, towncd
  , Counttown_cd = case 
      when row_number() over (partition by name,towncd,grp order by seqno) = 1 
        then count(*) over (partition by name,towncd, grp) 
      else null 
      end
from (
  select *
    , grp = row_number() over (partition by name,towncd order by seqno) 
          - row_number() over (order by seqno)
  from temp
    ) t
order by seqno

rextester 演示：http://rextester.com/VGXI71945

returns:

+-------+------+--------+--------------+
| seqno | name | towncd | Counttown_cd |
+-------+------+--------+--------------+
|     1 | man  |   0001 | 2            |
|     2 | man  |   0001 | NULL         |
|     3 | test |   0003 | 1            |
|     4 | man  |   0001 | 2            |
|     5 | man  |   0001 | NULL         |
+-------+------+--------+--------------+

原问题回答：

使用 case 表达式和两个 window 函数（row_number() 和 count(*) over()）仅显示 name,towncd 第一个实例的计数：

select seqno, name, towncd
  , Counttown_cd = case 
      when row_number() over (partition by name,towncd order by seqno) = 1 
        then count(*) over (partition by name,towncd) 
      else null 
      end
from temp

rextester 演示：http://rextester.com/NZSPR13395

returns:

+-------+------+--------+--------------+
| seqno | name | towncd | Counttown_cd |
+-------+------+--------+--------------+
|     1 | man  |   0001 | 2            |
|     2 | man  |   0001 | NULL         |
|     3 | test |   0003 | 1            |
+-------+------+--------+--------------+

使用 group by 计算 sql

Count in sql with group by

sql

sql-server

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