Question

一个用于现金，另一个用于阶段，具有以下结构

现金

FileID     Cash   Date
1           50   03.04.2017
2           100  08.07.2015
3           70   14.09.2018

阶段

FileID      Stage           Date_of_stage
1           Finished       06.04.2016
1           In Process     08.07.2015
2           Complication   17.08.2018
2           In Process     14.03.2018

尽管我的表有更多行。所以我要加入这两个表，因为我想使用以下选择按阶段将现金分组：

select fileID,  date, cash, max(date_of_stage) as max_date
from (select c.fileID, c.date, c.cash, s.stage, s.date_of_stage  
      from cash c
      inner join stage s
      on c.fileID=s.fileID
      and s.date_of_stage < c.date
      ) x
group by fileID, date, cash

我只需要max（date_of_stage），因为这对于我们的报告在逻辑上是合理的，而且这也不是问题的一部分。

问题是：当我比较现金表和上述选择项中的现金总额时，与上述现金项相比，我从上述选择项中获得的总金额少了一点表格（现金中的700万和上述选择中的6.9百万）。现在，我尝试使用左联接来识别丢失的记录：

select *
from (select fileID, date, cash
  from cash) x

left join 

(select fileID,  date, cash, max(date_of_stage) as max_date
from (select c.fileID, c.date, c.cash, s.stage, s.date_of_stage  
      from cash c
      inner join stage s
      on c.fileID=s.fileID
      and s.date_of_stage < c.date
      ) 
group by fileID, date, cash ) y
on x.fileID=y.fileID
and x.date=y.date
and x.cash=y.cash
where y.fileID is null

但是这个左联接没有给出任何内容，所以我无法识别和检查丢失的记录。有提示怎么办？

Answer 1

通过更改左表尝试以下操作

 select x.*

 (select fileID,  date, cash, max(date_of_stage) as max_date
    from (select c.fileID, c.date, c.cash, s.stage, s.date_of_stage  
          from cash c
          inner join stage s
          on c.fileID=s.fileID
          and s.date_of_stage < c.date
          ) 
    group by fileID, date, cash ) x left join 

     (select fileID, date, cash
      from cash) y    


    on x.fileID=y.fileID
    and x.date=y.date
    and x.cash=y.cash
    where y.fileID is null

Answer 2

我认为您需要做的是在原始查询中进行左外部联接，而不是内部联接，例如：

WITH cash AS (SELECT 1 fileid, 50 cash, to_date('03/04/2017', 'dd/mm/yyyy') dt FROM dual UNION ALL
              SELECT 2 fileid, 100 cash, to_date('08/07/2015', 'dd/mm/yyyy') dt FROM dual UNION ALL
              SELECT 3 fileid, 70 cash, to_date('14/09/2018', 'dd/mm/yyyy') dt FROM dual),
    stage AS (SELECT 1 fileid, 'Finished' stage, to_date('06/04/2016', 'dd/mm/yyyy') date_of_stage FROM dual UNION ALL
              SELECT 1 fileid, 'In Process' stage, to_date('08/07/2015', 'dd/mm/yyyy') date_of_stage FROM dual UNION ALL
              SELECT 2 fileid, 'Complication' stage, to_date('17/08/2018', 'dd/mm/yyyy') date_of_stage FROM dual UNION ALL
              SELECT 2 fileid, 'In Process' stage, to_date('14/03/2018', 'dd/mm/yyyy') date_of_stage FROM dual)
SELECT c.fileid,
       c.dt,
       c.cash,
       MAX(s.date_of_stage) max_date
FROM   cash c
       LEFT OUTER JOIN stage s ON c.fileid = s.fileid AND s.date_of_stage < c.dt
GROUP BY c.fileid,
         c.dt,
         c.cash;

    FILEID DT                CASH MAX_DATE
---------- ----------- ---------- -----------
         1 03/04/2017          50 06/04/2016
         2 08/07/2015         100 
         3 14/09/2018          70

Answer 3

这很奇怪。使用您提供的数据，“检查”查询可以正常工作并显示两行。这是dbfiddle demo。

无论如何，如果您只需要附加第二个表中的最大日期，请使用简单的子查询：

select fileID,  date_, cash, 
       (select max(date_of_stage) 
          from stage s
          where fileid = c.fileid and s.date_of_stage < c.date_) as max_date
  from cash c

^demo

左联接不返回缺少的信息-SQL Oracle

3 个答案: