SQL 服務器 CASE 表達式不會導致瀑布

Question

如果我有一個案例表達式，有沒有一種方法不能像瀑布一樣工作？

例如，如果我有以下數據集：

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

有沒有辦法可以顯示以下結果

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

以顯示

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

現在它顯示為

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

你可以使用聯合。

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%'