MySQL：同一查询中有两个移动平均线？

Question

是否有可能同时从同一个MySQL数据集中获得两个不同的移动平均线？

我正在尝试从MySQL数据库中提取数据，该数据库为我提供“原始”数据，以及相同数据集的两个不同移动平均值。我最好的尝试是在下面，问题是两个移动平均线似乎产生相同的结果？

此外，是否有更有效的查询数据方式？数据集相当大，这个查询运行时间太长了吗？

SELECT
  t1.`DateTime`,

  t1.`Positive` AS `RawData`,

(SELECT AVG(t2.`Positive`)
 FROM `tbl_DATA_KeywordResults` as t2
WHERE t2.`DateTime` <= t1.`DateTime`
ORDER BY t2.`DateTime` DESC
LIMIT 96
)  AS `DailyAverage`,

(SELECT AVG(t3.`Positive`)
FROM `tbl_DATA_KeywordResults` as t3
WHERE t3.`DateTime` <= t1.`DateTime`
ORDER BY t3.`DateTime` DESC
LIMIT 674
)  AS `WeeklyAverage`

FROM `tbl_DATA_KeywordResults` AS t1
ORDER BY t1.`DateTime`;

Answer 1

你在之后取平均值。子查询的正确形式是：

(select avg(Positive)
 from (SELECT t2.`Positive`
       FROM `tbl_DATA_KeywordResults` as t2
       WHERE t2.`DateTime` <= t1.`DateTime`
       ORDER BY t2.`DateTime` DESC
       LIMIT 96
      ) t
)  AS `DailyAverage`

我不是100％确定这可以作为子查询使用。我相信MySQL将外部引用（where子句中的内容）限制为一层深层。

在MySQL中有更多痛苦的方法：

select t1.DateTime, t1.RawData,
       avg(case when t2.DateTime between avg_96_dt and t1.DateTime then t2.Positive end) as avg96,
       avg(case when t2.DateTime between avg_674_dt and t1.DateTime then t2.Positive end) as avg674
from (SELECT t1.`DateTime`, t1.`Positive` AS `RawData`,
             (SELECT t2.DateTime
              FROM `tbl_DATA_KeywordResults` t2
              WHERE t2.`DateTime` <= t1.`DateTime`
              ORDER BY t2.`DateTime` DESC
              LIMIT 95, 1
             )  as avg_96_dt,
             (SELECT t2.DateTime
              FROM `tbl_DATA_KeywordResults` t2
              WHERE t2.`DateTime` <= t1.`DateTime`
              ORDER BY t2.`DateTime` DESC
              LIMIT 673, 1
             ) as avg_674_dt
      FROM `tbl_DATA_KeywordResults` t1
     ) t1 join
     tbl_DATA_KeywordResults t2
group by t1.DateTime, t1.RawData
ORDER BY t1.`DateTime`;

即，获取日期时间范围的限制，然后在不同的步骤中进行平均。