目前我有一个相当大的查询可以通过
- 通过获取按事件名称和日期分组的事件的
count()
,将每天、每周、每月的计数汇总到中间表中。 - 通过按事件进行
avg()
分组,选择每个中间表的平均计数,对结果进行联合,因为我想为每天、每周、每月设置一个单独的列,将填充值 0 放入空列中。 - 然后我对所有列求和,0 基本上充当空操作,这只为每个事件提供一个值。
虽然查询非常大,但我觉得我在做很多重复性工作。有什么办法可以更好地执行此查询或使其更小吗?我以前没有真正做过这样的查询,所以我不太确定。
WITH monthly_counts as (
SELECT
event,
count(*) as count
FROM tracking_stuff
WHERE
event = 'thing'
OR event = 'thing2'
OR event = 'thing3'
GROUP BY event, date_trunc('month', created_at)
),
weekly_counts as (
SELECT
event,
count(*) as count
FROM tracking_stuff
WHERE
event = 'thing'
OR event = 'thing2'
OR event = 'thing3'
GROUP BY event, date_trunc('week', created_at)
),
daily_counts as (
SELECT
event,
count(*) as count
FROM tracking_stuff
WHERE
event = 'thing'
OR event = 'thing2'
OR event = 'thing3'
GROUP BY event, date_trunc('day', created_at)
),
query as (
SELECT
event,
0 as daily_avg,
0 as weekly_avg,
avg(count) as monthly_avg
FROM monthly_counts
GROUP BY event
UNION
SELECT
event,
0 as daily_avg,
avg(count) as weekly_avg,
0 as monthly_avg
FROM weekly_counts
GROUP BY event
UNION
SELECT
event,
avg(count) as daily_avg,
0 as weekly_avg,
0 as monthly_avg
FROM daily_counts
GROUP BY event
)
SELECT
event,
sum(daily_avg) as daily_avg,
sum(weekly_avg) as weekly_avg,
sum(monthly_avg) as monthly_avg
FROM query
GROUP BY event;
最佳答案
我会这样写查询:
select event, daily_avg, weekly_avg, monthly_avg
from (
select event, avg(count) monthly_avg
from (
select event, count(*)
from tracking_stuff
where event in ('thing1', 'thing2', 'thing3')
group by event, date_trunc('month', created_at)
) s
group by 1
) monthly
join (
select event, avg(count) weekly_avg
from (
select event, count(*)
from tracking_stuff
where event in ('thing1', 'thing2', 'thing3')
group by event, date_trunc('week', created_at)
) s
group by 1
) weekly using(event)
join (
select event, avg(count) daily_avg
from (
select event, count(*)
from tracking_stuff
where event in ('thing1', 'thing2', 'thing3')
group by event, date_trunc('day', created_at)
) s
group by 1
) daily using(event)
order by 1;
如果 where
条件消除了很大一部分数据(比如一半以上),使用 cte
可以略微加快查询执行速度:
with the_data as (
select event, created_at
from tracking_stuff
where event in ('thing1', 'thing2', 'thing3')
)
select event, daily_avg, weekly_avg, monthly_avg
from (
select event, avg(count) monthly_avg
from (
select event, count(*)
from the_data
group by event, date_trunc('month', created_at)
) s
group by 1
) monthly
-- etc ...
出于好奇,我对数据进行了测试:
create table tracking_stuff (event text, created_at timestamp);
insert into tracking_stuff
select 'thing' || random_int(9), '2016-01-01'::date+ random_int(365)
from generate_series(1, 1000000);
在每个查询中,我都用 thing1
替换了 thing
,因此查询消除了大约 2/3 的行。
10 次测试的平均执行时间:
Original query 1106 ms
My query without cte 1077 ms
My query with cte 902 ms
Clodoaldo's query 5187 ms
关于sql - PostgreSQL 在一次查询中获取事件发生的每日、每周和每月平均值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38226788/