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mysql滑動(dòng)聚合/年初至今聚合原理與用法實(shí)例分析

更新時(shí)間：2019年12月27日 11:25:18 作者：雪山飛豬

這篇文章主要介紹了mysql滑動(dòng)聚合原理與用法,結(jié)合實(shí)例形式分析了mysql滑動(dòng)聚合的相關(guān)功能、原理、使用方法及操作注意事項(xiàng),需要的朋友可以參考下

本文實(shí)例講述了mysql滑動(dòng)聚合/年初至今聚合原理與用法。分享給大家供大家參考，具體如下：

滑動(dòng)聚合是按順序?qū)瑒?dòng)窗口范圍內(nèi)的數(shù)據(jù)進(jìn)行聚合的操作。下累積聚合不同，滑動(dòng)聚合并不是統(tǒng)計(jì)開始計(jì)算的位置到當(dāng)前位置的數(shù)據(jù)。

這里以統(tǒng)計(jì)最近三個(gè)月中員工第月訂單情況為例來介紹滑動(dòng)聚合。

滑動(dòng)聚合和累積聚合解決方案的主要區(qū)別在于連接的條件不同?；瑒?dòng)聚合條件不再是b.ordermonth <= a.ordermonth,而應(yīng)該是b.ordermonth大于前三個(gè)月的月份，并且小于當(dāng)前月份。因此滑動(dòng)聚合的解決方案的SQL語句如下

SELECT
 a.empid,
 DATE_FORMAT(a.ordermonth, '%Y-%m') AS ordermonth,
 a.qty AS thismonth,
 SUM(b.qty) AS total,
 CAST(AVG(b.qty) AS DECIMAL(5,2)) AS avg
FROM emporders a
INNER JOIN emporders b
 ON a.empid=b.empid
 AND b.ordermonth > DATE_ADD(a.ordermonth, INTERVAL -3 MONTH)
 AND b.ordermonth <= a.ordermonth
WHERE DATE_FORMAT(a.ordermonth,'%Y')='2015' AND DATE_FORMAT(b.ordermonth,'%Y')='2015'
GROUP BY a.empid,DATE_FORMAT(a.ordermonth, '%Y-%m'),a.qty
ORDER BY a.empid,a.ordermonth

運(yùn)行結(jié)果如下

該解決方案返回的是三個(gè)月為一個(gè)周期的滑動(dòng)聚合，但是每個(gè)用戶包含前兩個(gè)月并且未滿3個(gè)月的聚合。如果只希望返回滿3個(gè)月的聚合，不返回未滿3個(gè)月的聚合，可以使用HAVING過濾器進(jìn)行過濾，過濾的條件為MIN(b.ordermonth)=DATE_ADD(a.ordermonth, INTERVAL -2 MONTH),例如

SELECT
 a.empid,
 a.ordermonth AS ordermonth,
 a.qty AS thismonth,
 SUM(b.qty) AS total,
 CAST(AVG(b.qty) AS DECIMAL(5,2)) AS avg
FROM emporders a
INNER JOIN emporders b
 ON a.empid=b.empid
 AND b.ordermonth > DATE_ADD(a.ordermonth, INTERVAL -3 MONTH)
 AND b.ordermonth <= a.ordermonth
WHERE DATE_FORMAT(a.ordermonth,'%Y')='2015' AND DATE_FORMAT(b.ordermonth,'%Y')='2015' AND a.empid=1
GROUP BY a.empid,DATE_FORMAT(a.ordermonth, '%Y-%m'),a.qty
HAVING MIN(b.ordermonth)=DATE_ADD(a.ordermonth, INTERVAL-2 MONTH)
ORDER BY a.empid,a.ordermonth

運(yùn)行結(jié)果如下

年初至今聚合和滑動(dòng)聚合類似，不同的地方僅在于統(tǒng)計(jì)的僅為當(dāng)前一年的聚合。唯一的區(qū)別體現(xiàn)在下限的開始位置上。在年初至今的問題中，下限為該年的第一天，而滑動(dòng)聚合的下限為N個(gè)月的第一天。因此，年初至今的問題的解決方案如下圖所示，得到的結(jié)果

SELECT
 a.empid,
 DATE_FORMAT(a.ordermonth, '%Y-%m') AS ordermonth,
 a.qty AS thismonth,
 SUM(b.qty) AS total,
 CAST(AVG(b.qty) AS DECIMAL(5,2)) AS avg
FROM emporders a
INNER JOIN emporders b
  ON a.empid=b.empid
  AND b.ordermonth >= DATE_FORMAT(a.ordermonth, '%Y-01-01')
  AND b.ordermonth <= a.ordermonth
  AND DATE_FORMAT(b.ordermonth,'%Y')='2015'
GROUP BY a.empid,a.ordermonth,a.qty
ORDER BY a.empid,a.ordermonth

運(yùn)行結(jié)果如下