Question

我得到的示例SQL似乎无法满足我的需求。

大表有400万行，小表有60万行。

/ *示例代码：（我由一位高级分析师提供了此示例）* /

SELECT SUM(BigTable.VALUE)
        FROM BigTable INNER JOIN SmallTable
        WHERE BigTable.ID = SmallTable.ID
        AND BigTable.VALUATION_DATE IN 
                (SELECT MAX(VALUATION_DATE)
                FROM BigTable)
       GROUP BY BigTable.ID

/ *我的代码：（我在内部查询中放置了一个WHERE）* /

SELECT BigTable.ID, SUM(BigTable.VALUE)
        FROM BigTable INNER JOIN SmallTable
        WHERE BigTable.ID = SmallTable.ID
        AND BigTable.VALUATION_DATE IN 
                (SELECT MAX(VALUATION_DATE)
                FROM BigTable INNER JOIN SmallTable
                    WHERE BigTable.ID = SmallTable.ID)
       GROUP BY BigTable.ID

如果ID xyz在最近的日期具有三个分别值为$ 1，$ 2，$ 3的帐户，我想返回该日期所有帐户的总和：xyz，$ 6

Answer 1

因此，我认为您使用的INNER JOIN语法不正确。在将要连接的INNER JOIN表之后，您需要在ON上声明希望将表连接到哪些列。

以下查询是正确语法（尽管可能不适用于您的实现）。

SELECT BigTable.ID, SUM(BigTable.VALUE)
        FROM BigTable INNER JOIN SmallTable
        ON BigTable.ID = SmallTable.ID
        WHERE BigTable.VALUATION_DATE IN 
                (SELECT MAX(VALUATION_DATE)
                FROM BigTable INNER JOIN SmallTable
                    ON BigTable.ID = SmallTable.ID)
       GROUP BY BigTable.ID

仅当您执行交叉联接和自然联接时，才不使用ON关键字，而仅使用WHERE命令。

Answer 2

您应避免使用where子句，而应使用ON子句

SELECT SUM(BigTable.VALUE)
FROM BigTable 
INNER JOIN SmallTable ON  BigTable.ID = SmallTable.ID
AND BigTable.VALUATION_DATE =  (
    SELECT MAX(VALUATION_DATE)
    FROM BigTable)

并且您不应该使用ID为..

的分组

Answer 3

使用窗口功能：

SELECT b.ID, b.VALUE
FROM (SELECT b.*,
             ROW_NUMBER() OVER (PARTITION BY b.id ORDER BY b.VALUATION_DATE DESC) as seqnum
      FROM BigTable b
     ) b JOIN
     SmallTable s
     ON b.ID = s.ID
WHERE b.seqnum = 1;

我认为聚合不是必需的。但是，如果您在同一日期具有相同ID的多个值，则：

SELECT b.ID, SUM(b.VALUE)
FROM (SELECT b.*,
             RANK() OVER (PARTITION BY b.id ORDER BY b.VALUATION_DATE DESC) as seqnum
      FROM BigTable b
     ) b JOIN
     SmallTable s
     ON b.ID = s.ID
WHERE b.seqnum = 1
GROUP BY b.id;

内部查询中的最大值（日期）

3 个答案: