從多個表的字段創建摘要VIEW

Question

我正在嘗試編寫一個用於在MySQL中創建視圖的選擇查詢。 視圖中的每一行都應顯示從多個表收集的用戶值的每周摘要（總和，平均值）。 這些表彼此相似，但不相同。 該視圖還應包括行，以防其他表在該周沒有值。 像這樣：

| week_year | sum1 | avg1 | sum2 | user_id |
| --------- | ---- | ---- | ---- | ------- |
| 201840    |      |      | 3    | 1       |
| 201844    | 45   | 55   |      | 1       |
| 201845    | 55   | 65   |      | 1       |
| 201849    | 65   | 75   |      | 1       |
| 201849    | 75   | 85   | 3    | 2       |

---

這些表（簡化后）如下：

CREATE TABLE IF NOT EXISTS `t1` (
  `user_id` INT NOT NULL AUTO_INCREMENT,
  `date` DATE NOT NULL,
  `value1` int(3) NOT NULL,
  `value2` int(3) NOT NULL,
  PRIMARY KEY (`user_id`,`date`)
) DEFAULT CHARSET=utf8;

CREATE TABLE IF NOT EXISTS `t2` (
  `id` INT NOT NULL AUTO_INCREMENT,
  `date` DATE NOT NULL,
  `value3` int(3) NOT NULL,
  PRIMARY KEY (`id`)
) DEFAULT CHARSET=utf8;

CREATE TABLE IF NOT EXISTS `t3` (
  `t3_id` INT NOT NULL,
  `user_id` INT NOT NULL
) DEFAULT CHARSET=utf8;

我當前的解決方案似乎並不合理，我不確定在成千上萬行的情況下它將如何執行：

select ifnull(yearweek(q1.date1), yearweek(q1.date2)) as week_year,
       sum(value1)                             as sum1,
       avg(value2)                              as avg1,
       sum(value3)                                   as sum2,
       q1.user_id
from (select t2.date as date2,
             t1.date as date1,
             ifnull(t3.user_id, t1.user_id) as user_id,
             t1.value1,
             t1.value2,
             t2.value3
      from t2
             join t3 on t3.t3_id=t2.id
             left join t1 on yearweek(t1.date) = yearweek(t2.date) and t1.user_id = t3.user_id
      union
      select t2.date as date2,
             t1.date as date1,
             ifnull(t3.user_id, t1.user_id) as user_id,
             t1.value1,
             t1.value2,
             t2.value3
      from t2
             join t3 on t3.t3_id=t2.id
             right join t1 on yearweek(t1.date) = yearweek(t2.date) and t1.user_id = t3.user_id) as q1

group by week_year, user_id;

DB小提琴

當前解決方案在性能上是否還可以，還是有更好的選擇？ 如果將來添加了第三張（或第四張）表，我將如何管理查詢？ 我是否應該考慮創建一個單獨的表，並用觸發器對其進行更新？

提前致謝。

Answer 1

您可以執行的另一種方法是合並所有數據，然后將其分組。 您必須進行性能測試，看哪個更好：

SELECT

  yearweek(date), 
  SUM(value1) as sum1,
  AVG(value2) as avg1,
  SUM(value3) as sum2
FROM
(
  SELECT user_id, date, value1, value2, CAST(null as INT) as value3 FROM t1
  UNION ALL 
  SELECT user_id, date, null, null, value3 FROM t2 INNER JOIN t3 ON t2.id = t3.t3_id
)
GROUP BY
  user_id,
  yearweek(date)

希望mysql不會將null轉換為int的問題。