SQL變換合計值到各個列

Question

所以我有數據標準化這樣目前：

+----------+-------+-------+ 
| day  | color | value | 
+----------+-------+-------+ 
| 1/1/2016 | red | 1  | 
+----------+-------+-------+ 
| 1/1/2016 | blue | 2  | 
+----------+-------+-------+ 
| 1/1/2016 | green | 3  | 
+----------+-------+-------+ 
| 1/2/2016 | red | 4  | 
+----------+-------+-------+ 
| 1/2/2016 | blue | 5  | 
+----------+-------+-------+ 
| 1/2/2016 | green | 6  | 
+----------+-------+-------+ 

我想將其改造成這種佈局的報告：

+----------+-----+------+-------+ 
| day  | red | blue | green | 
+----------+-----+------+-------+ 
| 1/1/2016 | 1 | 2 | 3  | 
+----------+-----+------+-------+ 
| 1/2/2016 | 4 | 5 | 6  | 
+----------+-----+------+-------+ 

的代碼我使用這樣做是：

with 
red as (
    select 
    day 
    ,value as red 
    from mytable 
    where color='red' 
), 

blue as (
    select 
    day 
    ,value as blue 
    from mytable 
    where color='blue' 
), 

green as (
    select 
    day 
    ,value as green 
    from mytable 
    where color='green' 
) 

select 
red.* 
,blue.blue 
,green.green 
from red red 
inner join blue blue 
on red.day=blue.day 
inner join green green 
on red.day=green.day 

所以我的問題是，是否有一個更容易或不那麼羅嗦的方式來做到這一點在甲骨文？對於這樣一個簡單的任務似乎有點愚蠢！另外，這可能不是很有效。

Answer 1

希望，我正確理解你的問題。

我覺得下面的查詢會幫助你。

select day_col, 
max(case when color = 'red' then value_col end) red_color, 
max(case when color = 'blue' then value_col end) blue_color, 
max(case when color = 'green' then value_col end) green_color 
from your_table 
group by day_col;