SQL Server：如何包含可为空的分组值

我有以下SQL查询

SELECT
    cs.group,
    cs.code,
    ISNULL(SUM(CASE WHEN datepart(mm,cs.scheduledate) = 1 THEN cs.amount ELSE 0 END),0) as a_jan,
    ISNULL(SUM(CASE WHEN datepart(mm,cs.scheduledate) = 2 THEN cs.amount ELSE 0 END),0) as a_feb,
    ISNULL(SUM(CASE WHEN datepart(mm,cs.scheduledate) = 3 THEN cs.amount ELSE 0 END),0) as a_mar,
    ISNULL(SUM(CASE WHEN datepart(mm,cs.scheduledate) = 4 THEN cs.amount ELSE 0 END),0) as a_abr,
    ISNULL(SUM(CASE WHEN datepart(mm,cs.scheduledate) = 5 THEN cs.amount ELSE 0 END),0) as a_may,
    ISNULL(SUM(CASE WHEN datepart(mm,cs.scheduledate) = 6 THEN cs.amount ELSE 0 END),0) as a_jun,
    ISNULL(SUM(CASE WHEN datepart(mm,cs.scheduledate) = 7 THEN cs.amount ELSE 0 END),0) as a_jul,
    ISNULL(SUM(CASE WHEN datepart(mm,cs.scheduledate) = 8 THEN cs.amount ELSE 0 END),0) as a_ago,
    ISNULL(SUM(CASE WHEN datepart(mm,cs.scheduledate) = 9 THEN cs.amount ELSE 0 END),0) as a_sep,
    ISNULL(SUM(CASE WHEN datepart(mm,cs.scheduledate) = 10 THEN cs.amount ELSE 0 END),0) as a_oct,
    ISNULL(SUM(CASE WHEN datepart(mm,cs.scheduledate) = 11 THEN cs.amount ELSE 0 END),0) as a_nov,
    ISNULL(SUM(CASE WHEN datepart(mm,cs.scheduledate) = 12 THEN cs.amount ELSE 0 END),0) as a_dic,
    ISNULL(SUM(cs.amount),0) as a_cds
FROM
    employee_statement cs
WHERE
    datepart(yyyy,cs.startdate) = 2018
GROUP BY
    cs.group,
    cs.code

此查询返回如下表：

select g.group, c.code, . . .
from (select distinct group from employee_statement) g cross join
     (select distinct code from employee_statement) c left join
     employee_statement cs
     on cs.group = g.group and cs.code = c.code and
        cs.startdate >= '2018-01-01' and cs.startdate < '2019-01-01'
group by g.group, c.code;

GROUP是一个动态值，我可以对其进行硬编码，因为它不会发生太多变化，CODE是一个固定值列表

所以我需要的是，无论特定的

组

或

code

没有行，我都会得到值为0的行

例如：

---

有线索吗？谢谢

使用

交叉联接

生成行，使用

左联接

和

分组方式

获得所需的结果：

查询的结构如下所示：

select g.group, c.code, . . .
from (select distinct group from employee_statement) g cross join
     (select distinct code from employee_statement) c left join
     employee_statement cs
     on cs.group = g.group and cs.code = c.code and
        cs.startdate >= '2018-01-01' and cs.startdate < '2019-01-01'
group by g.group, c.code;

---

这既不需要

ISNULL（）

也不需要

COALESCE（）

（我的首选版本），因为您有

ELSE 0

。我认为

MONTH（）

比

DATEPART（）

更容易理解，谢谢。我用这种方法试过，结果也一样：）有什么线索吗？@VAAA。对

where

条件应该在

on

子句中（我更改了答案）。