我们有一个表,其中保存了给定(期间,志愿者)对的总在场时间,另一个记录了动作:我们知道动作发生在哪个现场。但我们不跟踪在给定上花费的时间行动。它不是一个很好的数据结构,但我无法改变它。
CREATE TABLE volunteer_presence (id integer, volunteer_id integer, minutes integer);
CREATE TABLE logged_actions (id integer, presence_id integer, section varchar);
我们想要做的是通过假设时间在给定状态下的所有动作之间平均分配来估算在给定动作上花费的时间。这不是很好,但我们很高兴至少拥有它。例如,假设我们有以下数据:
INSERT INTO volunteer_presence (id, volunteer_id, minutes) values (1, 333, 400);
INSERT INTO volunteer_presence (id, volunteer_id, minutes) values (2, 444, 90);
INSERT INTO volunteer_presence (id, volunteer_id, minutes) values (3, 555, 80);
INSERT INTO logged_actions (id, presence_id, section) values (10, 1, 'Cats');
INSERT INTO logged_actions (id, presence_id, section) values (11, 1, 'Dogs');
INSERT INTO logged_actions (id, presence_id, section) values (13, 1, 'Cats');
INSERT INTO logged_actions (id, presence_id, section) values (14, 1, 'Cats');
INSERT INTO logged_actions (id, presence_id, section) values (15, 1, 'Front');
INSERT INTO logged_actions (id, presence_id, section) values (16, 2, 'Dogs');
我们希望得到以下结果:
部分 | presence_id | 估计分钟 |
---|---|---|
猫 | 1 | 240.0 |
狗 | 1 | 80.0 |
正面 | 1 | 80.0 |
狗 | 2 | 90.0 |
例如(5 个动作中的 3 个)*400 是 240。
我想出的解决方案在 join 子句中有两个子查询时感觉不对。感觉它不会很好地扩展。
SELECT action_count_table.section,
action_count_table.presence_id,
((action_count_table.total_action_count / presence_total_actions.action_count) * time_table.minutes) AS estimated_minutes
FROM (
SELECT event.section AS section,
volunteer_presence.id AS presence_id,
SUM(event.action_count) AS total_action_count
FROM (
SELECT logged_actions.presence_id,
logged_actions.section,
COUNT(logged_actions.id) AS action_count
FROM logged_actions
GROUP BY logged_actions.presence_id, logged_actions.section
ORDER BY logged_actions.presence_id, logged_actions.section
) AS event
INNER JOIN volunteer_presence
ON volunteer_presence.id = event.presence_id
GROUP BY event.section, volunteer_presence.id
) AS action_count_table
INNER JOIN (
SELECT DISTINCT logged_actions.presence_id AS presence_id,
volunteer_presence.minutes AS minutes
FROM logged_actions
INNER JOIN volunteer_presence
ON volunteer_presence.id = logged_actions.presence_id
) AS time_table
ON action_count_table.presence_id = time_table.presence_id
INNER JOIN (
SELECT logged_actions.presence_id,
COUNT(logged_actions.id) AS action_count
FROM logged_actions
GROUP BY logged_actions.presence_id
ORDER BY logged_actions.presence_id
) AS presence_total_actions
ON presence_total_actions.presence_id = time_table.presence_id
是否有更好的解决方案,可以更好地扩展或至少更简单?
答案 0 :(得分:2)
SELECT
la.presence_id,
la.section,
vp.minutes * COUNT(*) / total -- 4
FROM (
SELECT
*,
COUNT(*) OVER (PARTITION BY presence_id) as total -- 1
FROM logged_actions
) la
JOIN volunteer_presence vp ON vp.id = la.presence_id -- 2
GROUP BY la.presence_id, la.section, la.total, vp.minutes -- 3
ORDER BY la.presence_id, la.section
COUNT()
window function 将每个 presence_id
的总计数添加到每条记录volunteer_presence
section
的每个 presence_id
的计数,除以之前计算的每个 total
的 presence_id
计数,然后乘以 minutes
。