即使该月没有数据，也要在每个月获取一行数据

Question

可以说我有一份销售报告：

Salesman | Sales | Month  | yr |
    A        5      1       2016
    A        12     1       2017
    A        3      1       2017
    A        25     5       2017
    B        20     4       2017
    B        49     6       2017

如果我想查看销售人员的总销售量，我将执行以下操作：

SELECT salesman, sum(SALES), MONTH from SALESTABLE GROUP BY Salesman, Mnth   where year = 2017

得到：

Salesman | Sales | Mnth | yr |
   A        15       1    2017
   A        25       5    2017
   B        20       4    2017
   B        49       6    2017

但是我想要以下内容：

Salesman | Sales | Mnth | yr   |
   A         15     1     2017
   A         0      2     2017
   A         0      3     2017
   ...
   A         25     5     2017
   ...

我尝试了以下方法：

DECLARE @MonthTable TABLE
(
Monthnumber int
)


DECLARE @cnt int = 0
while @cnt < 12
BEGIN
  SET @cnt = @cnt+1
  Insert into @MonthTable (monthnumber) values (@cnt)
END


SELECT salesman, 
    sum(SALES), 
    monthnumber 
FROM SALESTABLE
RIGHT JOIN @MonthTable ON monthnumber = mnth    
GROUP BY Salesman, monthnumber

但是，这正如预期的那样在“推销员”上给出了NULL 。

Answer 1

通过生成月份列表并交叉加入不同的销售人员和年份列表以重新加入表格，我们可以按生成的月份进行分组和汇总，如下所示：

;with months as (
  select Mnth 
  from (values(1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11),(12)) t(Mnth)
)
select 
    s.Salesman
  , s.Yr
  , m.Mnth
  , Sales = coalesce(sum(t.Sales),0)
from (
  select distinct Salesman, yr
  from t
  ) as s
  cross join months m
  left join t
    on s.Salesman = t.Salesman
    and s.Yr = t.Yr
    and m.Mnth = t.[Month]
where s.yr = 2017
group by s.Salesman, s.Yr, m.Mnth

extrester演示： http ：//rextester.com/ZOHB53144

收益：

+----------+------+------+-------+
| Salesman |  Yr  | Mnth | Sales |
+----------+------+------+-------+
| A        | 2017 |    1 |    15 |
| A        | 2017 |    2 |     0 |
| A        | 2017 |    3 |     0 |
| A        | 2017 |    4 |     0 |
| A        | 2017 |    5 |    25 |
| A        | 2017 |    6 |     0 |
| A        | 2017 |    7 |     0 |
| A        | 2017 |    8 |     0 |
| A        | 2017 |    9 |     0 |
| A        | 2017 |   10 |     0 |
| A        | 2017 |   11 |     0 |
| A        | 2017 |   12 |     0 |
| B        | 2017 |    1 |     0 |
| B        | 2017 |    2 |     0 |
| B        | 2017 |    3 |     0 |
| B        | 2017 |    4 |    20 |
| B        | 2017 |    5 |     0 |
| B        | 2017 |    6 |    49 |
| B        | 2017 |    7 |     0 |
| B        | 2017 |    8 |     0 |
| B        | 2017 |    9 |     0 |
| B        | 2017 |   10 |     0 |
| B        | 2017 |   11 |     0 |
| B        | 2017 |   12 |     0 |
+----------+------+------+-------+

Answer 2

正如您正确地创建了一个月表以提供那些没有销售的月份的月条目一样，您需要一个主业务员表来为销售员提供那些没有销售的月份的信息。

以最简单的形式，您可以通过获取distinct salesman从salesdata表生成主业务员表； 理想情况下，您可能希望使用一个单独的销售员表，每个销售员都有一个条目。

该查询将变为：

SELECT salesman, 
    sum(SALES), 
    monthnumber 
FROM SALESTABLE
RIGHT JOIN @MonthTable ON monthnumber = mnth    
GROUP BY Salesman, monthnumber

SELECT 
    salesmanlist.salesman 
  , SUM(salestable.sales) 
  , monthtable.monthnumber 
FROM 
  (SELECT DISTINCT salesman FROM salestable) as salesmanlist   --   <-- Key change 
  CROSS JOIN @MonthTable as monthtable 
  LEFT JOIN salestable 
    ON     salesmanlist.salesman = salestable.salesman 
       AND salestable.mnth = monthtable.monthnumber