Question

我有一个名为maximo_audit的表，我试图只计算最新的actiondate记录，其中包含N的批准状态。我写了这个查询，但它需要永远运行

SELECT COUNT (*)
  FROM (SELECT   MAX (actiondate)
            FROM timedetail t JOIN maximo_audit m ON m.recordid = t.quantity
           WHERE approvalstatus = 'N'
             AND t.tsdate BETWEEN '8-dec-2013' AND '21-dec-2013'
             AND task2 IS NOT NULL
        --and recordid = '1781891'
        GROUP BY m.recordid
          HAVING MAX (actiondate) IN (SELECT MAX (actiondate)
                                        FROM maximo_audit ma
                                       WHERE ma.recordid = m.recordid))

Answer 1

通常使用显式连接有助于优化器。您还可以使用更简单的count(distinct)替换子查询。

  SELECT COUNT(DISTINCT m.recordid)
  FROM timedetail t JOIN
       maximo_audit m
       ON m.recordid = t.quantity JOIN
       (select ma.recordid, max(actiondate) as actiondate
        from maximo_audit ma
        group by ma.recordid
       ) ma
       on ma.recordid = m.recordid and ma.actiondate = m.actiondate
  WHERE approvalstatus = 'N' AND
        t.tsdate BETWEEN '8-dec-2013' AND '21-dec-2013' AND
        task2 IS NOT NULL;

having子句可以用连接替换，因为当操作日期的最大值等于某个值时，其中一个操作日期将匹配该值。

Oracle Max Date查询

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