SQL 服务器 CASE 表达式不会导致瀑布

Question

如果我有一个案例表达式，有没有一种方法不能像瀑布一样工作？

例如，如果我有以下数据集：

group    value
---------------
derek    5
cait     1
david    2
denver   3

有没有办法可以显示以下结果

CASE 
    WHEN group like 'd%' then d
    WHEN group like 'de% then de
    ELSE other

以显示

group  value
--------------
d      10
de     8
other  3

现在它显示为

group  value
--------------
d      10
other  2

Answer 1

您可以改用left join ：

select coalesce(which, 'other'), sum(t.value)
from t left join
     (values ('d%', 'd'), ('de%', 'de')
     ) v(pattern, which)
     on t.group like v.pattern
group by which;

Answer 2

你可以使用联合。

SELECT 'd' [group], SUM(Value)[Value] FROM <table_name> WHERE [GROUP] LIKE 'd%'
UNION
SELECT 'de' [group], SUM(Value)[Value] FROM <table_name> WHERE [GROUP] LIKE 'de%'
UNION
SELECT 'other' [group], SUM(Value)[Value] FROM <table_name> WHERE [GROUP] NOT LIKE 'd%' OR [GROUP] NOT LIKE 'de%'