如何使用重复的子查询优化大查询

时间：2010-11-19 14:34:06

标签： mysql query-optimization subquery correlated-subquery

我有以下包含重复子查询的巨大查询，对我来说效率看起来非常低效。我该如何优化呢？

SELECT T2.date1, T2.date2, T2.period, T1.market, T1.ticker, 0 AS scenario
FROM
(SELECT  DISTINCT
        Q.market AS market,
        Q.ticker AS ticker

FROM portfolio.scenario S RIGHT JOIN portfolio.quote Q
ON    S.series =  (SELECT S.series
                  FROM scenario S
                  WHERE S.date1 >= '2009-09-01' AND
                        S.date2 <= '2010-07-01' AND
                        S.period = 'QUARTER'
                  ORDER BY S.date2
                  LIMIT 1) AND
      Q.market = S.market AND 
      Q.ticker = S.ticker

WHERE  Q.date = '2010-07-01' AND
       S.date1 IS NULL) AS T1

JOIN 

(SELECT DISTINCT S.date1, S.date2, S.period
FROM scenario S
WHERE S.series = (SELECT S.series
                  FROM scenario S
                  WHERE S.date1 >= '2009-09-01' AND
                        S.date2 <= '2010-07-01' AND
                        S.period = 'QUARTER'
                  ORDER BY S.date2
                  LIMIT 1) AND
      S.date1 >= '2009-09-01' AND
      S.date2 <= '2010-07-01') AS T2

UNION

SELECT  S.date1 AS date1, 
        S.date2 AS date2,
        S.period AS period,
        Q.market AS market,
        Q.ticker AS ticker,
        Q.close * EXP(S.ratio) AS scenario

FROM portfolio.scenario S , portfolio.quote Q

WHERE  S.series = (SELECT S.series
                  FROM scenario S
                  WHERE S.date1 >= '2009-09-01' AND
                        S.date2 <= '2010-07-01' AND
                        S.period = 'QUARTER'
                  ORDER BY S.date2
                  LIMIT 1) AND
      S.date1 >= '2009-09-01' AND
      S.date2 <= '2010-07-01' AND
      Q.date = '2010-07-01' AND
      Q.market = S.market AND 
      Q.ticker = S.ticker

UNION

SELECT T2.date1, T2.date2, T2.period, T1.market, T1.ticker, 0 AS scenario
FROM
(SELECT  DISTINCT
        Q.market AS market,
        Q.ticker AS ticker

        FROM portfolio.scenario S , portfolio.quote Q
        WHERE  Q.date = '2010-07-01' AND
              Q.market = S.market AND 
              Q.ticker = S.ticker AND
              S.series = (SELECT S.series
                  FROM scenario S
                  WHERE S.date1 >= '2009-09-01' AND
                        S.date2 <= '2010-07-01' AND
                        S.period = 'QUARTER'
                  ORDER BY S.date2
                  LIMIT 1) AND
              S.date1 >= '2009-09-01' AND
              S.date2 <= '2010-07-01' ) AS T1

JOIN 

(SELECT DISTINCT S.date1, S.date2, S.period
FROM scenario S
WHERE S.series = (SELECT S.series
                  FROM scenario S
                  WHERE S.date1 >= '2009-09-01' AND
                        S.date2 <= '2010-07-01' AND
                        S.period = 'QUARTER'
                  ORDER BY S.date2
                  LIMIT 1) AND
      S.date1 >= '2009-09-01' AND
      S.date2 <= '2010-07-01') AS T2


WHERE (T2.date1, T2.date2, T2.period, T1.market, T1.ticker)
        NOT IN (SELECT  S.date1 AS date1, 
                S.date2 AS date2,
                S.period AS period,
                Q.market AS market,
                Q.ticker AS ticker

        FROM portfolio.scenario S , portfolio.quote Q
        WHERE  Q.date = '2010-07-01' AND
              Q.market = S.market AND 
              Q.ticker = S.ticker AND
              S.series = (SELECT S.series
                  FROM scenario S
                  WHERE S.date1 >= '2009-09-01' AND
                        S.date2 <= '2010-07-01' AND
                        S.period = 'QUARTER'
                  ORDER BY S.date2
                  LIMIT 1) AND
              S.date1 >= '2009-09-01' AND
              S.date2 <= '2010-07-01' )


ORDER BY 
date1,date2,period,market,ticker

在@ Bruce的评论和减少子查询的一些逻辑后，我的查询现在是：

(SELECT S.date1, 
        S.date2,
        S.period,
        Q.market,
        Q.ticker,
        Q.close * EXP(S.ratio) AS scenario

FROM portfolio.scenario S , portfolio.quote Q

WHERE  
      S.date1 >= (@date1 := '2009-09-01') AND
      S.date2 <= (@date2 := '2010-07-01') AND
      Q.date = (@qdate := '2010-07-01') AND
      S.series = 
      (@series := 
                  (SELECT S.series
                  FROM scenario S
                  WHERE S.date1 >= '2009-09-01' AND
                        S.date2 <= '2010-07-01' AND
                        S.period = 'QUARTER'
                  ORDER BY S.date2
                  LIMIT 1)) AND
      Q.market = S.market AND 
      Q.ticker = S.ticker)

UNION

(SELECT T2.date1, T2.date2, T2.period, T1.market, T1.ticker, 0 AS scenario
FROM
(SELECT Q.market, Q.ticker
 FROM quote Q
 WHERE Q.date = @qdate) AS T1

JOIN 

(SELECT DISTINCT S.date1, S.date2, S.period
FROM scenario S
WHERE S.series = @series AND
      S.date1 >= @date1 AND
      S.date2 <= @date2) AS T2

WHERE (T2.date1, T2.date2, T2.period, T1.market, T1.ticker)
        NOT IN 

        (SELECT  S.date1,
                 S.date2,
                 S.period,
                 Q.market,
                 Q.ticker
        FROM portfolio.scenario S , portfolio.quote Q
        WHERE  Q.date = @qdate AND
               Q.market = S.market AND 
               Q.ticker = S.ticker AND
               S.series = @series AND
               S.date1 >= @date1 AND
               S.date2 <= @date2 ))

然而，如果我改变了

  (@series := 
              (SELECT S.series
              FROM scenario S
              WHERE S.date1 >= '2009-09-01' AND
                    S.date2 <= '2010-07-01' AND
                    S.period = 'QUARTER'
              ORDER BY S.date2
              LIMIT 1))

是

  (@series := 
              (SELECT S.series
              FROM scenario S
              WHERE S.date1 >= @date1 AND
                    S.date2 <= @date2 AND
                    S.period = 'QUARTER'
              ORDER BY S.date2
              LIMIT 1))

处理它需要太多时间（我在10分钟前执行了查询但仍然没有得到结果），而查询通常会在5秒后返回。

此外，当我重置变量时，执行结果不正确（可能使用上一次执行中的变量值）。如何在不添加SET语句的情况下进行更改（我希望它是单个查询）

1 个答案:

答案 0 :(得分：4)

使用MySQL变量：

SELECT
    @x := ColumnName,
    @y := ColumnName2 + @z,
    @z := (SELECT * FROM SubTable WHERE x = @x),
    (SELECT * FROM Table2 WHERE X = @z),
    (SELECT * FROM Table3 WHERE X = @z)
FROM Table
WHERE
    v = @v
  • 您可以将子选择和列值分配给SQL变量
  • 您可以在声明
    • 中的任何位置引用这些变量
  • 变量包含先前行（如果已设置）
    • 的值
  • 您可以这种方式重复使用子选择和其他值
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