SQL格式化行列

Question

您好我有這樣一個表：

c1 c2 c3 c4 c5 
v1 xx xx a 1 
v1 xx xx b 2 
v2 xx xx a 3 
v3 xx xx a 2 
v3 xx xx b 1 

我想根據C4值，除去C4和轉讓C5成2列：

c1 c2 c3 c5_a c5_b 
v1 xx xx 1  2 
v2 xx xx 3  0 
v3 xx xx 2  1 

如何做到這一點在SQL中？

Answer 1

這是VKP的回答輕微的調整，但它是一個有點簡單：

select c1, c2, c3, 
     max(case when c4 = 'a' then c5 else 0 end) as c5_a, 
     max(case when c4 = 'b' then c5 else 0 end) as c5_b 
from t 
group by c1, c2, c3; 

而且，目前還不清楚是否要max()或sum()。

注意：這裏假設xx值在每一行中都是相同的。否則，您可能還需要這些聚合函數：

select c1, max(c2) as c2, max(c3) as c3, 
     max(case when c4 = 'a' then c5 else 0 end) as c5_a, 
     max(case when c4 = 'b' then c5 else 0 end) as c5_b 
from t 
group by c1; 

Answer 2

這可以通過條件聚合來完成，假設分組列是c1，c2，c3。

select c1,c2,c3, 
coalesce(max(case when c4='a' then c5 end),0) as c5_a, 
coalesce(max(case when c4='b' then c5 end),0) as c5_b 
from t 
group by c1,c2,c3