MySQL：同一查询中有两个移动平均线？

Question

Is it possible to get two different moving averages from the same MySQL dataset at the same time?

I'm trying to extract data from a MySQL database that gives me the 'raw' data, plus two different moving averages of the same data set. My best attempt is below, the problem is that the two moving averages appear to be producing identical results?

Also, is there a more efficient way of querying the data? The dataset is reasonably large and this query takes a little too long to run?

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

You are taking the limit after you do the average. The correct form of the subquery would be:

(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`

I'm not 100% sure that this will work as a subquery. I believe MySQL limits outer references (what's in the where clause) to one layer deep.

There are more painful ways of doing this in MySQL:

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`;

That is, get the limits for the date time range and then do the average in a different step.