如何在SQL查詢中聚合兩類值？

Question

我有一個包含間隔表：

CREATE TABLE tbl (
    user_id: INTEGER, 
    start: TIMESTAMP, 
    end: TIMESTAMP, 
    billable: BOOLEAN 
); 

我想創建一個類似如下的觀點：

user_id | billable_time | unbillable_time 

我可以用這樣的查詢得到這兩個一個：

SELECT user_id, sum(end - start) AS billable_time WHERE billable = TRUE GROUP BY user_id; 

但是，我需要兩個列，其中不可壓縮的時間是等效的：

SELECT user_id, sum(end - start) AS unbillable_time WHERE billable = FALSE GROUP BY user_id; 

如何將這兩個值合併到一個查詢中？

Answer 1

select user_id, sum(case billable when 1 then (end - start) end) as can_bill, 
    sum(case billable when 0 then (end - start) end) as unbillable 

Answer 2

SELECT user_id, billable, sum(end - start) AS billable_time 
GROUP BY user_id,billable;