用過濾列PostgreSQL視圖

Question

我有這樣的一個表：

date_added  owner  action 
01-02-2016  1   note 
04-02-2016  1   call 
04-02-2016  1   call 
05-02-2016  1   note 
05-02-2016  1   meeting 
06-02-2016  1   meeting 
06-02-2016  1   note 
06-02-2016  1   cal 
06-02-2016  1   note 
10-02-2016  1   call 
10-02-2016  1   note 
10-02-2016  1   meeting 

我需要這樣一個觀點：

date_added  owner  note  call  meeting 
01-02-2016  1   1   0   0 
04-02-2016  1   0   2   0 
05-02-2016  1   0   0   1 
06-02-2016  1   2   1   1 
10-02-2016  1   1   1   1 

我如何創建一個列有類似

WHERE action LIKE 'note' 

？

Answer 1

您可以使用CASE表達式。

查詢

select date_added, owner, 
sum(case action when 'note' then 1 else 0 end) note, 
sum(case action when 'call' then 1 else 0 end) call, 
sum(case action when 'meeting' then 1 else 0 end) meeting 
from your_table_name 
group by date_added, owner; 

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