5

代码

以下代码针对大量数据计算线性回归的斜率和截距。然后,它将方程应用于y = mx + b相同的结果集,以计算每一行的回归线的值。

如何连接这两个查询,以便在不执行该WHERE子句两次的情况下计算数据及其斜率/截距?

问题的一般形式是:

SELECT a.group, func(a.group, avg_avg)
FROM a
    (SELECT AVG(field1_avg) as avg_avg
     FROM (SELECT a.group, AVG(field1) as field1_avg
           FROM a
           WHERE (SOME_CONDITION)
           GROUP BY a.group) as several_lines -- potentially
    ) as one_line -- always
WHERE (SOME_CONDITION)
GROUP BY a.group -- again, potentially several lines

我已经SOME_CONDITION执行了两次。如下所示(通过STRAIGHT_JOIN优化更新):

SELECT STRAIGHT_JOIN
  AVG(D.AMOUNT) as AMOUNT,
  Y.YEAR * ymxb.SLOPE + ymxb.INTERCEPT as REGRESSION_LINE,
  Y.YEAR as YEAR,
  MAKEDATE(Y.YEAR,1) as AMOUNT_DATE,
  ymxb.SLOPE,
  ymxb.INTERCEPT,
  ymxb.CORRELATION,
  ymxb.MEASUREMENTS
FROM
  CITY C,
  STATION S,
  STATION_DISTRICT SD,
  YEAR_REF Y,
  MONTH_REF M,
  DAILY D,
  (SELECT
    SUM(MEASUREMENTS) as MEASUREMENTS,

    ((sum(t.YEAR) * sum(t.AMOUNT)) - (count(1) * sum(t.YEAR * t.AMOUNT))) /
    (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as SLOPE,

    ((sum( t.YEAR ) * sum( t.YEAR * t.AMOUNT )) -
    (sum( t.AMOUNT ) * sum(power(t.YEAR, 2)))) /
    (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as INTERCEPT,

    ((avg(t.AMOUNT * t.YEAR)) - avg(t.AMOUNT) * avg(t.YEAR)) /
    (stddev( t.AMOUNT ) * stddev( t.YEAR )) as CORRELATION
  FROM (
    SELECT STRAIGHT_JOIN
      COUNT(1) as MEASUREMENTS,
      AVG(D.AMOUNT) as AMOUNT,
      Y.YEAR as YEAR
    FROM
      CITY C,
      STATION S,
      STATION_DISTRICT SD,
      YEAR_REF Y,
      MONTH_REF M,
      DAILY D
    WHERE
      -- For a specific city ...
      --
      $X{ IN, C.ID, CityCode } AND

      -- Find all the stations within a specific unit radius ...
      --
      6371.009 *
      SQRT(
        POW(RADIANS(C.LATITUDE_DECIMAL - S.LATITUDE_DECIMAL), 2) +
        (COS(RADIANS(C.LATITUDE_DECIMAL + S.LATITUDE_DECIMAL) / 2) *
         POW(RADIANS(C.LONGITUDE_DECIMAL - S.LONGITUDE_DECIMAL), 2)) ) <= $P{Radius} AND

      SD.ID = S.STATION_DISTRICT_ID AND

      -- Gather all known years for that station ...
      --
      Y.STATION_DISTRICT_ID = SD.ID AND

      -- The data before 1900 is shaky; insufficient after 2009.
      --
      Y.YEAR BETWEEN 1900 AND 2009 AND

      -- Filtered by all known months ...
      --
      M.YEAR_REF_ID = Y.ID AND

      -- Whittled down by category ...
      --
      M.CATEGORY_ID = $P{CategoryCode} AND

      -- Into the valid daily climate data.
      --
      M.ID = D.MONTH_REF_ID AND
      D.DAILY_FLAG_ID <> 'M'
    GROUP BY
      Y.YEAR
  ) t
) ymxb
WHERE
  -- For a specific city ...
  --
  $X{ IN, C.ID, CityCode } AND

  -- Find all the stations within a specific unit radius ...
  --
  6371.009 *
  SQRT(
    POW(RADIANS(C.LATITUDE_DECIMAL - S.LATITUDE_DECIMAL), 2) +
    (COS(RADIANS(C.LATITUDE_DECIMAL + S.LATITUDE_DECIMAL) / 2) *
     POW(RADIANS(C.LONGITUDE_DECIMAL - S.LONGITUDE_DECIMAL), 2)) ) <= $P{Radius} AND

  SD.ID = S.STATION_DISTRICT_ID AND

  -- Gather all known years for that station ...
  --
  Y.STATION_DISTRICT_ID = SD.ID AND

  -- The data before 1900 is shaky; insufficient after 2009.
  --
  Y.YEAR BETWEEN 1900 AND 2009 AND

  -- Filtered by all known months ...
  --
  M.YEAR_REF_ID = Y.ID AND

  -- Whittled down by category ...
  --
  M.CATEGORY_ID = $P{CategoryCode} AND

  -- Into the valid daily climate data.
  --
  M.ID = D.MONTH_REF_ID AND
  D.DAILY_FLAG_ID <> 'M'
GROUP BY
  Y.YEAR

问题

如何每次查询只执行一次重复位,而不是两次?重复代码:

  $X{ IN, C.ID, CityCode } AND
  6371.009 *
  SQRT(
    POW(RADIANS(C.LATITUDE_DECIMAL - S.LATITUDE_DECIMAL), 2) +
    (COS(RADIANS(C.LATITUDE_DECIMAL + S.LATITUDE_DECIMAL) / 2) *
     POW(RADIANS(C.LONGITUDE_DECIMAL - S.LONGITUDE_DECIMAL), 2)) ) <= $P{Radius} AND
  SD.ID = S.STATION_DISTRICT_ID AND
  Y.STATION_DISTRICT_ID = SD.ID AND
  Y.YEAR BETWEEN 1900 AND 2009 AND
  M.YEAR_REF_ID = Y.ID AND
  M.CATEGORY_ID = $P{CategoryCode} AND
  M.ID = D.MONTH_REF_ID AND
  D.DAILY_FLAG_ID <> 'M'
GROUP BY
  Y.YEAR

更新 1

使用变量和拆分查询似乎允许缓存启动,因为它现在在 3.5 秒内运行,而它曾经在 7 秒内运行。不过,如果有任何方法可以删除重复的代码,我将不胜感激帮助。

更新 2

上面的代码不能在 JasperReports 中运行,而 VIEW 虽然是一种可能的修复方法,但可能效率极低(因为 WHERE 子句是参数化的)。

更新 3

使用 Unreason 建议的勾股公式与收敛子午线验证距离:

  6371.009 *
  SQRT(
    POW(RADIANS(C.LATITUDE_DECIMAL - S.LATITUDE_DECIMAL), 2) +
    (COS(RADIANS(C.LATITUDE_DECIMAL + S.LATITUDE_DECIMAL) / 2) *
    POW(RADIANS(C.LONGITUDE_DECIMAL - S.LONGITUDE_DECIMAL), 2)) )

(这与问题无关,但其他人是否想知道......)

更新 4

如图所示,代码在 JasperReports 中运行,针对 MySQL 数据库运行。JasperReports 不允许变量或多个查询。

更新 5

我正在寻找一个干净执行的解决方案。;-) 我写了一些部分工作的解决方案,但遗憾的是,MySQL 不理解部分正确。请参阅与 Unreason 的讨论,以获得几乎可行的答案。

更新 6

我也许可以重用第一个子句中的变量WHERE并将它们与第二个子句进行比较(从而消除一些重复——对$P{}值的检查),但我真的很希望消除重复。

更新 7

比较YEAR子句,如先前更新中假设的那样,以消除重复BETWEEN,不起作用。

有关的

如何消除 SQL 中的重复计算?

谢谢!

4

4 回答 4

5

您应该能够一口气获得所需的一切:

 SELECT
    AVG(D.AMOUNT) as AMOUNT,
    Y.YEAR as YEAR,
    MAKEDATE(Y.YEAR,1) as AMOUNT_DATE,
    Y.YEAR * ymxb.SLOPE + ymxb.INTERCEPT as REGRESSION_LINE,             
    ((avg(AVG(D.AMOUNT) * Y.YEAR)) - avg(AVG(D.AMOUNT)) * avg(Y.YEAR)) /                  
    (stddev( AVG(D.AMOUNT) ) * stddev( Y.YEAR )) as CORRELATION,                     
    ((sum(Y.YEAR) * sum(AVG(D.AMOUNT))) - (count(1) * sum(Y.YEAR * AVG(D.AMOUNT)))) /
    (power(sum(Y.YEAR), 2) - count(1) * sum(power(Y.YEAR, 2))) as SLOPE,   
    ((sum( Y.YEAR ) * sum( Y.YEAR * AVG(D.AMOUNT) )) -
    (sum( AVG(D.AMOUNT) ) * sum(power(Y.YEAR, 2)))) / 
    (power(sum(Y.YEAR), 2) - count(1) * sum(power(Y.YEAR, 2))) as INTERCEPT
 FROM
    CITY C,
    STATION S,
    YEAR_REF Y,
    MONTH_REF M,
    DAILY D
 WHERE
    $X{ IN, C.ID, CityCode } AND
    SQRT(
        POW( C.LATITUDE - S.LATITUDE, 2 ) +
        POW( C.LONGITUDE - S.LONGITUDE, 2 ) ) < $P{Radius} AND
    S.STATION_DISTRICT_ID = Y.STATION_DISTRICT_ID AND
    Y.YEAR BETWEEN 1900 AND 2009 AND
    M.YEAR_REF_ID = Y.ID AND
    M.CATEGORY_ID = $P{CategoryCode} AND
    M.ID = D.MONTH_REF_ID AND
    D.DAILY_FLAG_ID <> 'M'
 GROUP BY
    Y.YEAR

这些事情不会直接从上面的查询中起作用(它有无意义的组​​合聚合和其他错误);这可能是检查您的公式的好时机

如果您决定进行子查询确实简化了公式,那么:

  • 您可以在最内部的查询中抓取(您确实抓取)所有必要的数据,并且您不必再重复外部查询中的所有表(只需从 t 中选择相关的列,它们已经可供您使用)
  • 您不必重复 where 条件
于 2010-05-10T08:10:29.983 回答
1

这个问题比你的概括要困难一些。我会这样说:

SELECT a.group, func(a.group, avg_avg)
FROM a
    (SELECT AVG(field1_avg) as avg_avg
     FROM (SELECT a.group, AVG(field1) as field1_avg
           FROM a
           WHERE (YOUR_CONDITION)
           GROUP BY a.group) as several_lines -- potentially
    ) as one_line -- always
WHERE (YOUR_CONDITION)
GROUP BY a.group -- again, potentially several lines

您有一个数据子集(受您的条件限制),它被分组并为每个组进行聚合。然后,您将向下聚合合并为单个值,并且您希望将该值的函数再次应用于每个组。显然,在分组子查询的结果可以作为实体引用之前,您不能重用条件。

在 MSSQL 和 Oracle 中,您将使用WITH运算符。在 MySQL 中,唯一的选择是使用临时表。我假设您的报告中有超过一年的时间(否则,查询会简单得多)。

UPD:对不起,我现在不能发布现成的代码(明天可以做),但我有一个想法:

您可以使用, 和函数将需要在子查询中输出的数据连接起来,GROUP_CONCAT并将其拆分回外部查询中。外部查询将仅加入 YEAR_REF 和聚合结果。FIND_IN_SETSUBSTRING_INDEX

外部查询中的条件将是 just WHERE FIND_IN_SET(year, concatenated_years)

更新

这是使用 GROUP_CONCAT 将所需数据传递给外部 JOIN 的版本。

我的评论以--newtover:. 顺便说一句,1)我认为 STRAIGHT_JOIN 不会增加任何好处,并且 2)COUNT(*)在 MySQL 中具有特殊含义,应该在您想要计算行数时使用。

SELECT STRAIGHT_JOIN
  -- newtover: extract the corresponding amount back
  SUBSTRING_INDEX(SUBSTRING_INDEX(GROUPED_AMOUNTS, '|', @pos),'|', -1) as AMOUNT,
  Y.YEAR * ymxb.SLOPE + ymxb.INTERCEPT as REGRESSION_LINE,
  Y.YEAR as YEAR,
  MAKEDATE(Y.YEAR,1) as AMOUNT_DATE,
  ymxb.SLOPE,
  ymxb.INTERCEPT,
  ymxb.CORRELATION,
  ymxb.MEASUREMENTS
FROM
  -- newtover: list of tables now contains only the subquery, YEAR_REF for grouping and init_vars to define the variable
  YEAR_REF Y,
  (SELECT
    SUM(MEASUREMENTS) as MEASUREMENTS,
    ((sum(t.YEAR) * sum(t.AMOUNT)) - (count(1) * sum(t.YEAR * t.AMOUNT))) /
    (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as SLOPE,
    ((sum( t.YEAR ) * sum( t.YEAR * t.AMOUNT )) -
    (sum( t.AMOUNT ) * sum(power(t.YEAR, 2)))) /
    (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as INTERCEPT,
    ((avg(t.AMOUNT * t.YEAR)) - avg(t.AMOUNT) * avg(t.YEAR)) /
    (stddev( t.AMOUNT ) * stddev( t.YEAR )) as CORRELATION,
    -- newtover: grouped fields for matching years and the corresponding amounts
    GROUP_CONCAT(Y.YEAR) as GROUPED_YEARS,
    GROUP_CONCAT(AMOUNT SEPARATOR '|') as GROUPED_AMOUNTS
  FROM (
    SELECT STRAIGHT_JOIN
      COUNT(1) as MEASUREMENTS,
      AVG(D.AMOUNT) as AMOUNT,
      Y.YEAR as YEAR
    FROM
      CITY C,
      STATION S,
      STATION_DISTRICT SD,
      YEAR_REF Y,
      MONTH_REF M,
      DAILY D
    WHERE
      -- For a specific city ...
      $X{ IN, C.ID, CityCode } AND
      -- Find all the stations within a specific unit radius ...
      6371.009 *
      SQRT(
        POW(RADIANS(C.LATITUDE_DECIMAL - S.LATITUDE_DECIMAL), 2) +
        (COS(RADIANS(C.LATITUDE_DECIMAL + S.LATITUDE_DECIMAL) / 2) *
         POW(RADIANS(C.LONGITUDE_DECIMAL - S.LONGITUDE_DECIMAL), 2)) ) <= $P{Radius} AND
      SD.ID = S.STATION_DISTRICT_ID AND
      -- Gather all known years for that station ...
      Y.STATION_DISTRICT_ID = SD.ID AND
      -- The data before 1900 is shaky; insufficient after 2009.
      Y.YEAR BETWEEN 1900 AND 2009 AND
      -- Filtered by all known months ...
      M.YEAR_REF_ID = Y.ID AND
      -- Whittled down by category ...
      M.CATEGORY_ID = $P{CategoryCode} AND
      -- Into the valid daily climate data.
      M.ID = D.MONTH_REF_ID AND
      D.DAILY_FLAG_ID <> 'M'
    GROUP BY
      Y.YEAR
  ) t
) ymxb,
(SELECT @pos:=NULL) as init_vars
WHERE
    -- newtover: check if the year is in the list and store the index into the variable
    @pos:=CAST(FIND_IN_SET(Y.YEAR, GROUPED_YEARS) as UNSIGNED)
GROUP BY
  Y.YEAR
于 2010-05-14T23:52:10.337 回答
0

由于问题中的 SQL 已被大量挂起(现在仅显示相关部分),这是我的新答案

假设:条件确实相同,子查询和外部查询之间没有出现棘手的列别名

答:您可以删除外部查询中的 where。

SELECT
  /* aggregate data */
  ymxb.*
FROM (
  SELECT
    /* similar aggregate data */
  WHERE
    /* some condition */
  GROUP BY
    YEAR
) ymxb
GROUP BY
  YEAR

这应该会给你同样的结果。

(另请注意,您可以删除内部位置并保留外部位置 - 结果应该相同,但性能可能不同)。

最后,重复 where 子句可能不会对性能产生太大影响- 与任何 I/O 相比,评估额外条件(甚至是诸如 sqrt 等表达式)非常便宜(并且这些条件不会对任何新列进行操作,所以所有 I/O 都已完成)

此外,您的内部查询和外部查询使用相同的 GROUP BY,外部查询从子查询中获取所有数据。

这使得外部查询中的任何聚合函数都是多余的(来自子查询的行,它们是外部查询的源,已经按年份分组)。

这使得整个子选择变得多余。

于 2010-05-11T10:58:01.293 回答
0

你能在你的情况下使用临时表吗?尽管它仍然要求您使用 WHERE 子句两次,但它应该会大大提高您的性能。

DROP TEMPORARY TABLE IF EXISTS TEMP_DATA

CREATE TEMPORARY TABLE TEMP_DATA 
    (SELECT AVG(field1_avg) as avg_avg
     FROM (SELECT a.group, AVG(field1) as field1_avg
           FROM a
           WHERE (SOME_CONDITION)
           GROUP BY a.group)
    )

SELECT t.group, func(t.group, t.avg_avg)
FROM TEMP_DATA AS t
WHERE (SOME_CONDITION)
GROUP BY t.group

希望这可以帮助!--配音

于 2010-05-18T12:06:09.237 回答