SQL：在同一字段中使用不同where子句的2個不同計數

Question

如何將以下2個查詢合併到一個查詢中？

select count(distinct user_id) as action_1_count, date 
from table  
where action = "action_1" 
group by date; 

select count(distinct user_id) as action_2_count, date 
from table 
where action = "action_2" 
group by date; 

Answer 1

SELECT COUNT(user_id), date 
FROM table 
WHERE action IN ('action_1', 'action_2) 
GROUP BY action, date 

Answer 2

您的查詢，可就是這樣

SELECT COUNT(user_id), date FROM table WHERE action IN ('action_1', 'action_2') GROUP BY date 

下面是使用SUM()功能本應該做的伎倆

SELECT 
    SUM(action ='action_1') count_1, 
    SUM(action ='action_2') count_2, 
    SUM(action ='action_1' OR action ='action_2') `full_count`, 
    date 
FROM 
table 
GROUP BY date 

與表達式中使用SUM()將導致另一條路在布爾值中，如果action ='action_1'那麼結果將是1如果沒有的話0，這一切都歸結生產基於表達式的結果計數

Answer 3

做這樣的合併上面的查詢：

SELECT date, 
     CASE WHEN action = "action_1" THEN COUNT(user_id) END AS Action1Count, 
     CASE WHEN action = "action_2" THEN COUNT(user_id) END AS Action2Count 
    FROM table  
    WHERE action IN ("action_1", "action_2") 
    GROUP BY date 

Answer 4

以上答案會給你ACTION_2多行，而看起來你只需要一行action_2。

你可以使用一個聯盟：

select '1', count(distinct user_id), date 
from table 
where action = "action_1" 
group by 3 
union 
select '2', count(distinct user_id), max(date) 
from table 
where action = "action_2" 
group by 3;