問題描述

我在這里設置了一個小提琴:https://www.db-fiddle.com/f/snDGExYZgoYASvWkDGHKDC/2

I've setup a fiddle here: https://www.db-fiddle.com/f/snDGExYZgoYASvWkDGHKDC/2

還有:

架構:

CREATE TABLE `scores` (
  `id` bigint unsigned NOT NULL AUTO_INCREMENT,
  `shift_id` int unsigned NOT NULL,
  `employee_name` varchar(255) COLLATE utf8mb4_unicode_ci NOT NULL,
  `score` double(8,2) unsigned NOT NULL,
  `created_at` timestamp NOT NULL,
  PRIMARY KEY (`id`)
);

INSERT INTO scores(shift_id, employee_name, score, created_at) VALUES
(1, "John",   6.72, "2020-04-01 00:00:00"),
(1, "Bob",   15.71, "2020-04-01 00:00:00"),
(1, "Bob",   54.02, "2020-04-01 08:00:00"),
(1, "John",  23.55, "2020-04-01 13:00:00"),
(2, "John",   9.13, "2020-04-02 00:00:00"),
(2, "Bob",   44.76, "2020-04-02 00:00:00"),
(2, "Bob",   33.40, "2020-04-02 08:00:00"),
(2, "James", 20,    "2020-04-02 00:00:00"),
(3, "John",  20,    "2020-04-02 00:00:00"),
(3, "Bob",   20,    "2020-04-02 00:00:00"),
(3, "Bob",   30,    "2020-04-02 08:00:00"),
(3, "James", 10,    "2020-04-02 00:00:00")

查詢 1:

-- This doesn't work

SELECT
    employee_name,
    DATE_FORMAT(created_at, '%Y-%m-%d') AS `date`,
    ANY_VALUE(AVG(score) OVER(PARTITION BY(ANY_VALUE(created_at)))) AS `average_score`
FROM
  scores
GROUP BY
    employee_name, date;

查詢 2:

SELECT
    employee_name,
    DATE_FORMAT(created_at, '%Y-%m-%d') AS `date`,
    ANY_VALUE(AVG(score)) AS `average_score`
FROM
  scores
GROUP BY
    employee_name, date;

查詢 3:

-- This works but scales very poorly with millions of rows

SELECT
    t1.employee_name,
    ANY_VALUE(DATE_FORMAT(t1.created_at, '%Y-%m-%d')) AS `date`,
    ANY_VALUE(SUM(t1.score) / (
      SELECT SUM(t2.score)
      FROM scores t2
      WHERE date(t2.created_at) = date(t1.created_at)
    ) * 100) AS `average_score`
FROM
  scores t1
GROUP BY
    t1.employee_name, date;

第三個查詢正確執行，但在我的測試中，當擴展到數百萬行時非常慢.我認為這是因為它是一個相關的子查詢并且運行了數百萬次.

The third query executes correctly but in my testing has been very slow when scaling to millions of rows. I think this is because it is a correlated subquery and runs millions of times.

前兩次嘗試是我嘗試創建以使用 MySQL 8 Window Functions 對平均計算進行分區.然而，這些正在產生意想不到的結果.給定日期的 average_score 總數應該加起來為 100，就像在第三個查詢中一樣.

The first two attempts are me trying to created to use MySQL 8 Window Functions to partition the average calculation. However, these are giving unexpected results. The total average_scores for a given day should add up to 100, like it does in the 3rd query.

有人知道更有效的計算方法嗎?

Does anyone know of a more efficient way to calculate this?

還值得注意的是，在現實中，查詢中也會有一個 WHERE IN 以按特定的 shift_id 進行過濾.給定的 shift_ids 數量可以是幾十萬，也可以是一百萬.

It's also worth noting that in reality, there will also be a WHERE IN on the queries to filter by specific shift_ids. The number of shift_ids given could be in the hundreds of thousands, up to a million.

正在考慮的另一件事是 ElasticSearch.是否有助于更快地計算這些?

One other thing being considered is ElasticSearch. Would it help with calculating these in a quicker way?

推薦答案

您可以使用窗口函數.訣竅是取每個員工每天總分的窗口總和，如下所示:

You can use window functions. The trick is to take a window sum of the total score per employee for each day, like so:

select
    employee_name,
    date(created_at) created_date,
    100 * sum(score) / sum(sum(score)) over(partition by date(created_at)) monthly_score
from scores
group by employee_name, date(created_at)

在你的數據庫小提琴中，這個產量:

In your DB Fiddle, this yields:

| employee_name | created_date | monthly_score |
| ------------- | ------------ | ------------- |
| John          | 2020-04-01   | 30.27         |
| Bob           | 2020-04-01   | 69.73         |
| John          | 2020-04-02   | 15.55342      |
| Bob           | 2020-04-02   | 68.42864      |
| James         | 2020-04-02   | 16.01794      |

這篇關于MySQL 8 按日期分區計算平均值的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！