Question

我在 ms access 中为三个表写了一个查询＆＃34; Process Name＆＃34;，＆＃34; Work_Log1＆＃34;和＆＃34; ACn_reviewer＆＃34;。

现在＆＃34; Work_Log1＆＃34; table正在使用＆＃34; Process NAme＆＃34;和＆＃34; ACN_REviewer＆＃34;表。

但是＆＃34; Work_log1＆＃34; table在某些行中具有空值，用于＆＃34; ACN_Reviewer＆＃34;表

正在运作查询我想出了

select w.[activity_id], w.[activity_start_date], w.[reporting month] , 
r.[Reviewer_Name] , p.[process_name]
from [process name] p left join 
([work_log1] w left join [acn_reviewer] r
on w.[ACN Reviwer] = r.[ACN_Reviewer_ID]  )
on w.[process] = p.[process_id] 
 where w.[activity_id] = 54447

现在我知道work_log1表中没有进程ids null。

我问的问题是，在没有连接的情况下，有哪些方法可以进行上述查询？

像这样的东西，只在acn_reviewer上加入

 select w.[activity_id], w.[activity_start_date], w.[reporting month] , 
r.[Reviewer_Name] , p.[process_name]
from [process name] p  ,   [work_log1] w left join [acn_reviewer] r
 on w.[ACN Reviwer] = r.[ACN_Reviewer_ID]   
  where w.[process] = p.[process_id] and 
  w.[activity_id] = 54447

我希望现在我很清楚

所以我可以在sql中写这样的东西，这会在ms-access中抛出错误

select w.[activity_id], w.[activity_start_date], w.[reporting month] ,
r.[Reviewer_Name] , p.[process_name] from [process name] p, [work_log1] w 
left join [acn_reviewer] r
on w.[ACN Reviwer] = r.[ACN_Reviewer_ID]  on w.[process] = p.[process_id]
 where w.[activity_id] = 54447 ;

由于

Pradyut

Answer 1

从我从上面的属性中收集的内容：

Process Name (p)
p.[process_name]
p.[process_id]

Work_Log1 (w)
w.[activity_id]
w.[process]
w.[acn reviwer]
w.[activity_start_date]
w.[reporting month]

ACN Reviewer (r)
r.[acn_reviewer_id]
r.[reviewer_name]

Process Name和ACN Reviewer如何相关？如果不是，则无法根据NULL中的Work_Log1值来桥接它们。

Answer 2

最后一次尝试：我正在考虑....也许你想把这些结果联合到另一个选择，其中work_log1左连接到acn_reviewer（没有首先加入work_log1）以获取情况process为null且acn_reviewer不是？是？没有...？谁知道。我累了。访问不允许完整的外连接和东西......也许这就是你想要做的，实际上？

        select  pw.[activity_id], 
                pw.[activity_start_date], 
                pw.[reporting month] ,
                r.[Reviewer_Name], 
                pw.[process_name] 

        from    ([work_log1] as w

                join [process name] as p 
                on w.[process] = p.[process_id] ) as pw

                    join [acn_reviewer] as r
                    on pw.[ACN Reviwer] = r.[ACN_Reviewer_ID]  

        where   pw.[activity_id] = 54447 

        -- all records in work_log1 that have a matching row both
                    -- in acn_reviewer and process via the join 

        union 


        select  pw.[activity_id], 
                pw.[activity_start_date], 
                pw.[reporting month] ,
                null as [Reviewer_Name], 
                pw.[process_name] 

        from    ([work_log1] as w

                join [process name] as p 
                on w.[process] = p.[process_id] ) as pw

                    left join [acn_reviewer] as r
                    on pw.[ACN Reviwer] = r.[ACN_Reviewer_ID]  

        where   pw.[activity_id] = 54447 and r.[acn reviewer] is null

        -- all records where work_log1, WITH a row in process, 
                    -- WITHOUT a row in acn_reviewer 

        union

        select  pw.[activity_id], 
                pw.[activity_start_date], 
                pw.[reporting month] ,
                r.[Reviewer_Name] as [Reviewer_Name], 
                null as [process_name] 

        from    ([work_log1] as w

                join [acn_reviewer] as r
                on w.[ACN Reviwer] = r.[ACN_Reviewer_ID] ) as wr

                    left join [process name] as p 
                    on w.[process] = p.[process_id]  

        where   pw.[activity_id] = 54447 and p.[process_id] is null

        -- all records where work_log1, WITHOUT a row in process, 
                    -- WITH a row in acn_reviewer 

        union


        select  pw.[activity_id], 
                pw.[activity_start_date], 
                pw.[reporting month] ,
                null as [Reviewer_Name], 
                null as [process_name] 

        from    ([work_log1] as w

                left outer join [acn_reviewer] as r
                on w.[ACN Reviwer] = r.[ACN_Reviewer_ID]  ) as wr

                    left outer join [process name] as p 
                    on wr.[process] = p.[process_id]

        where   pw.[activity_id] = 54447 and p.[process_id] is null and wr.[ACN_Reviewer_ID] is null

        -- all records in work_log1 that have no matching rows in either process or acn_reviewier
                    --  cuzzz its a left outer join and the where says the joined tables return null-thing

访问是奇怪的，如果你将整个事情放入select * from (query with unions) as x where activity_id = 54447但是我不确定，可能会也可能不会喜欢它。我没有测试过这个。但你希望得到这个想法。希望这就是你想要的。 * IF NOT ---＆gt;像njk这样的ERD提供了我们/你是正确的（b / c你说他错了）会非常有帮助，没有它或没有示例结果集，它显示你需要的NULL我就是无法继续。 *

或...你的第一个查询被剥离了连接？

select  w.[activity_id], 
        w.[activity_start_date], 
        w.[reporting month], 
        r.[Reviewer_Name], 
        p.[process_name]

from    work_log1 as w, acn_reviewer as r, process as p 

where   (w.[acn reviewer] = r.acn_reviewer_id or r.acn_reviewer_id is null) and 
        w.process = p.process_id

替换访问sql中的多个左连接

2 个答案: