Question

通过查看其他示例无法在此处连接点。寻找一些帮助写这个，以便它只撤回每个9DVN的最新条目：也就是说，拉回最近生效日期的一行数据。

    SELECT b.vndr_name AS Supplier,
           a.VENDOR_NBR*1000 + a.VENDOR_DEPT_NBR*10 + a.VENDOR_SEQ_NBR AS "9DVN", 
           a.VENDOR_NBR AS "6DVN",a.VENDOR_DEPT_NBR AS "Dept", 
           a.VENDOR_SEQ_NBR AS "Seq" ,a.FREIGHT_FACTOR_PCT AS "Rate",
           a.Effective_Date AS "Effect Date",
           a.LAST_CHANGE_USERID AS "By",
           COUNT(a.DC_NBR) AS "DC Count"
  FROM MainTable.DC_FRT_FCTR a
  INNER JOIN SecondaryTable ON b.vndr_nbr = a.vendor_nbr
  ORDER BY a.Effective_Date DESC
  GROUP BY B.vndr_name, 
  a.VENDOR_NBR, 
  a.VENDOR_DEPT_NBR, 
  a.VENDOR_SEQ_NBR,  
  a.FREIGHT_FACTOR_PCT, 
  Effective_Date, 
  a.LAST_CHANGE_USERID

Answer 1

这是一种常见的查询模式：查找与特定列的极值相关联的详细信息行。

您需要一个子查询来查找每个供应商的极值 - 在您的情况下是最新生效日期。像这样：

                   SELECT MAX(Effective_Date) Effective_Date,
                          VENDOR_NBR*1000 + VENDOR_DEPT_NBR*10 + VENDOR_SEQ_NBR "9DVN"  
                     FROM DC_FRT_FCTR 
                 GROUP BY VENDOR_NBR*1000 + VENDOR_DEPT_NBR*10 + VENDOR_SEQ_NBR

您应该测试此子查询以确保它产生合理的结果。

然后你需要将它加入到极值的其余查询中，就像这样。

   SELECT b.vndr_name AS Supplier,
          a.VENDOR_NBR*1000 + a.VENDOR_DEPT_NBR*10 + a.VENDOR_SEQ_NBR AS "9DVN", 
          ...etc...
          COUNT(a.DC_NBR) AS "DC Count"
     FROM MainTable.DC_FRT_FCTR a
     JOIN (
                   SELECT MAX(Effective_Date) Effective_Date,
                          VENDOR_NBR*1000 + VENDOR_DEPT_NBR*10 + VENDOR_SEQ_NBR "9DVN"  
                     FROM DC_FRT_FCTR 
                 GROUP BY VENDOR_NBR*1000 + VENDOR_DEPT_NBR*10 + VENDOR_SEQ_NBR
          ) latest 
              ON latest.9DVN = a.VENDOR_NBR*1000 + a.VENDOR_DEPT_NBR*10 + a.VENDOR_SEQ_NBR
             AND latest.Effective_Date = a.Effective_Date
     JOIN SecondaryTable b 
              ON b.vndr_nbr = a.vendor_nbr
 ORDER BY a.Effective_Date DESC
 GROUP BY B.vndr_name, 
          ... etc ...

在mysql中返回最新的“effective_date”行

1 个答案: