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      计算移动平均 MySQL?

      时间:2023-06-02
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                本文介绍了计算移动平均 MySQL?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着跟版网的小编来一起学习吧!

                问题描述

                美好的一天,

                我正在使用以下代码来计算 9 天移动平均线.

                I am using the following code to calculate the 9 Day Moving average.

                SELECT SUM(close)
                FROM tbl
                WHERE date <= '2002-07-05'
                AND name_id = 2
                ORDER BY date DESC
                LIMIT 9
                

                但它不起作用,因为它在调用限制之前首先计算所有返回的字段.换句话说,它将计算该日期之前或等于该日期的所有收盘价,而不仅仅是最后 9 个.

                But it does not work because it first calculates all of the returned fields before the limit is called. In other words it will calculate all the closes before or equal to that date, and not just the last 9.

                所以我需要根据返回的选择计算 SUM,而不是直接计算.

                So I need to calculate the SUM from the returned select, rather than calculate it straight.

                浏览器.从 SELECT... 中选择 SUM...

                IE. Select the SUM from the SELECT...

                现在我该怎么做,它是非常昂贵的还是有更好的方法?

                Now how would I go about doing this and is it very costly or is there a better way?

                推荐答案

                使用类似的东西

                SELECT 
                  sum(close) as sum,
                  avg(close) as average
                FROM (
                    SELECT 
                      (close)
                    FROM 
                      tbl
                    WHERE 
                      date <= '2002-07-05'
                      AND name_id = 2
                    ORDER BY 
                      date DESC
                    LIMIT 9 ) temp
                

                内部查询以desc的顺序返回所有过滤的行,然后你avgsum把返回的那些行加起来.

                The inner query returns all filtered rows in desc order, and then you avg, sum up those rows returned.

                你给出的query不工作的原因是先计算sumLIMITsum 已经计算之后应用子句,为您提供所有存在行的 sum

                The reason why the query given by you doesn't work is due to the fact that the sum is calculated first and the LIMIT clause is applied after the sum has already been calculated, giving you the sum of all the rows present

                这篇关于计算移动平均 MySQL?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持跟版网!

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