删除冗余的SQL代码

时间：2010-05-10 00:43:35

标签： sql mysql postgresql ireport code-duplication

代码

以下代码计算线性回归与斜率数据的斜率和截距。然后，它将等式y = mx + b应用于相同的结果集，以计算每行的回归线的值。

如何连接两个查询以便计算数据及其斜率/截距而不执行WHERE子句两次？

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SOME_CONDITION执行了两次。如下所示（使用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？重复的代码：

  $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

使用变量并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中运行。但是，如果有任何方法可以删除重复的代码，我会感谢任何帮助。

<击> 更新2

上面的代码不能在JasperReports中运行，而VIEW虽然可能是一个修复，但效率可能非常低（因为WHERE子句是参数化的）。

更新3

使用Unreason对具有收敛经络的毕达哥拉斯公式的建议来验证距离：

  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利落的解决方案。 ;-)我已经写了一些部分工作的解决方案，但遗憾的是，MySQL不理解部分正确的。请参阅与Unreason的讨论，了解几乎可行的答案。

更新6

我或许能够重用第一个WHERE子句中的变量并将它们与第二个进行比较（从而消除一些重复 - 对$P{}值的检查），但我真的希望删除重复。

更新7

比较前一次更新中假设的YEAR子句，以消除重复的BETWEEN，不起作用。

相关

How to eliminate duplicate calculation in SQL?

谢谢！

4 个答案:

答案 0 :(得分：5)

您应该能够一次性获得所需的一切：

 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

将无法直接从上面的查询中运行（它具有无意义的组​​合聚合和其他错误）;这是检查公式的好时机

如果您决定进行子查询，请简化公式，然后：

  • 你可以抓住（你抓住）最内层查询中的所有必要数据，你不必再重复外部查询中的所有表格了（只需从t中选择相关列，它们已经是在你的处置）
  • 您不必重复where where条件

答案 1 :(得分：1)

这个问题比你的概括要困难一些。我会说如下：

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），该数据被分组并为每个组进行聚合。然后，将聚合合并到单个值，并且您希望再次将值的函数应用于每个组。显然，在分组子查询的结果可以作为实体引用之前，您不能重用该条件。

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一年以上（否则，查询会更简单）。

UPD ：很抱歉，我现在无法发布现成的代码（可以明天发布），但我有个主意：

您可以将子查询中需要输出的数据与GROUP_CONCAT连接起来，并使用FIND_IN_SET和SUBSTRING_INDEX函数将其拆分回外部查询中。外部查询将只加入YEAR_REF和聚合结果。

外部查询中的条件将只是WHERE FIND_IN_SET(year, concatenated_years)。

<强> UPD ：

以下是使用GROUP_CONCAT将所需数据传递到外部JOIN的版本。

我的评论以--newtover:开头。顺便说一下，1）我不认为STRAIGHT_JOIN会增加任何好处，2）COUNT(*)在MySQL中有特殊含义，而应该在你想要计算行时使用。

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

答案 2 :(得分：0)

由于问题中的SQL被大幅挂起（现在只显示相关部分），这是我的新答案

假设：条件实际上是相同的，子查询和外部查询之间没有棘手的列别名

答案： 您可以删除外部查询中的位置。

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

这应该会给你相同的结果。

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

最后，重复where子句可能对性能没有太大影响 - 评估额外条件（甚至表达式，如sqrt等）与任何I / O相比都非常便宜（这些条件不能在任何新列上运行，因此所有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，外部查询从子查询获取所有数据。

这使得外部查询中的任何聚合函数都是冗余的（来自子查询的行，它们是外部查询的源，已按年分组）。

这使整个子选择变得多余。

答案 3 :(得分：0)

您是否可以在您的情况下使用临时表？虽然它仍然需要你两次使用WHERE子句，但它应该会大大提高你的性能。

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

希望这有帮助！ --Dubs

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