如何在SQL查询中聚合两类值？

Question

我有一个包含间隔的表格：

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

我想创建一个如下所示的视图：

user_id | billable_time | unbillable_time

我可以使用如下查询获取这两个中的一个：

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

但是，我需要两个列，无法计时的时间相当于：

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

如何将这两个值合并到一个查询中？

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;