Sql server 如何在T-SQL中按空值分组

在

SELECT

语句中，我需要知道

Coverage

列中是否有

NULL

；如果是这样，那么我希望它替换为不为NULL的值和GROUP BY

declare @TestTable table 
(
     ClaimNumber varchar(50), 
     Status varchar(50),
     Coverage varchar(50),
     Losses money
)

insert into @TestTable 
values ('WICCACA0000002', 'Open', 'Auto BIPD',5000),
       ('WICCACA0000003', 'Closed', 'Collision', 1000),
       ('WICCACA0000003', 'Closed', NULL, 2000)

select 
    ClaimNumber,
    Status,
    Coverage,
    SUM(Losses) as Losses 
from 
    @TestTable
group by 
    ClaimNumber, Status, Coverage

结果如下所示：

ClaimNumber     Status  Coverage    Losses
--------------------------------------------
WICCACA0000002  Open    Auto BIPD   5000.00
WICCACA0000003  Closed  NULL        2000.00
WICCACA0000003  Closed  Collision   1000.00

但我需要这样的结果：

ClaimNumber     Status  Coverage    Losses
--------------------------------------------
WICCACA0000002  Open    Auto BIPD   5000.00
WICCACA0000003  Closed  Collision   3000.00

我认为

coalesce（）

可以满足您的需求：

select ClaimNumber, Status, coalesce(Coverage, 'Collision') as coverage
       SUM(Losses) as Losses 
from @TestTable
group by ClaimNumber, Status, coalesce(Coverage, 'Collision');

或者，如果

Coverage

中只有一个值（如在示例数据中），只需使用聚合函数：

select ClaimNumber, Status, max(Coverage) as coverage
       SUM(Losses) as Losses 
from @TestTable
group by ClaimNumber, Status;

---

但如果有多行具有不同的非空值，则选择哪一行？谢谢，完全忘记了MAX（）函数