ClickHouse聚合-组按日/月/年(时间戳)?

Question

是否有办法在ClickHouse做一个组按日/月/年()与时间戳值?在为ClickHouse重写MySQL查询时很难弄清楚。我的MySQL查询看起来像这样…

SELECT COUNT(this), COUNT(that) FROM table WHERE something = x AND stamp BETWEEN startdate AND enddate
SELECT COUNT(this), COUNT(that) FROM table WHERE something = x AND stamp BETWEEN startdate AND enddate GROUP BY DAY(stamp)
SELECT COUNT(this), COUNT(that) FROM table WHERE something = x AND stamp BETWEEN startdate AND enddate GROUP BY MONTH(stamp)
SELECT COUNT(this), COUNT(that) FROM table WHERE something = x AND stamp BETWEEN startdate AND enddate GROUP BY YEAR(stamp)

在MySQL中非常简单和缓慢，但我不知道如何在ClickHouse中做聚合。

谢谢!

Answer 1

使用toYear, tommonth, toDayOfMonth函数获取日期的一部分:

SELECT
toMonth(time) AS month,
count()
FROM 
(
SELECT
number,
addDays(now(), number) AS time
FROM numbers(8)
)
GROUP BY month
/*
┌─month─┬─count()─┐
│     1 │       7 │
│     2 │       1 │
└───────┴─────────┘
*/

---

使用WITH ROLLUP-modifier:

SELECT
toYear(time) AS year,
toMonth(time) AS month,
toDayOfMonth(time) AS day,
count()
FROM 
(
SELECT
number,
addDays(now(), number) AS time
FROM numbers(8)
)
GROUP BY
year,
month,
day
WITH ROLLUP
/*
┌─year─┬─month─┬─day─┬─count()─┐
│ 2021 │     2 │   1 │       1 │ // day
│ 2021 │     1 │  29 │       1 │ // day
│ 2021 │     1 │  31 │       1 │ // day
│ 2021 │     1 │  26 │       1 │ // day
│ 2021 │     1 │  25 │       1 │ // day
│ 2021 │     1 │  28 │       1 │ // day
│ 2021 │     1 │  30 │       1 │ // day
│ 2021 │     1 │  27 │       1 │ // day
│ 2021 │     1 │   0 │       7 │ // month
│ 2021 │     2 │   0 │       1 │ // month
│ 2021 │     0 │   0 │       8 │ // year
│    0 │     0 │   0 │       8 │
└──────┴───────┴─────┴─────────┘
*/