union all 后只返回一条记录

Question

使用 SQL 接口进入 AS/400 (iSeries) DB2 数据库，但遇到并发出托盘信息可以存储在两个表中的位置，一个用于未分配库存(warpall)，另一个用于分配股票(warpalq)。 如果适用，我需要从两个表中返回记录。

warpalq 只有少数几个与warpall 相关的字段 我需要来自warpall 的字段之一也用于加入另一个表，warpalq 中没有相关字段。

我使用union 在一个结果集中从两个表返回数据，然后加入其他表。

问题是，当在结果集上加入第三个表 (warcmdt) 时，它在 commpm 和 fdsccd 字段中有空值 / 0，因为它在相应的表中没有相应的数据。

有没有办法可以将commpm 和fdsccd 拉回第2 行的结果集中？ 交叉链接为pal#pm = pal#pq，因此存在相对链接。

运行下面的 SQL 会返回这个结果集。

select 
clntwf, commpm, fdsccd, clsqwf, pal#wf, dtcdpm, clsswf, srb#pm, descsc, 
cor#or  

from
(select substr(warpall.clntpm,1,2) as clntwf, pal#pm as pal#wf, commpm, 
substr(warpall.clsspm,1,2) as clsswf, warpall.clsqpm * 1 as clsqwf, srb#pm, 
dtcdpm, srd#pm 
from warpall

where 
locnpm <> 'ASSEMBLED PALLET'
and commpm <> 'ASSEMBLED PALLET'
and clsqpm <> 0
and clntPM <> 'D2'
and pal#pm = '1005609592'

union all

select substr(clntpq,1,2) as clntwf, pal#Pq as pal#wf, '0', 
substr(clsspq,1,2) as clsswf, clsqpq * 1 as clsqwf, '0', '0', '0' 
from warpalq

where 
clsqpq <> 0
and clntPQ <> 'D2'
and pal#pq = '1005609592'

) as t9

left outer join warcmdt as t3
on 
t3.clntcd = t9.clntwf  and t3.commcd = t9.commpm

left join
warclss as t4
on
t4.clsssc = t9.clsswf

left join
warohrh as t5
on
t5.clntor = t9.clntwf 
and t5.srn#or = t9.srd#pm

order by pal#wf asc

Answer 1

您可以尝试像这样使用公用表表达式 (CTE)：

with 
  pal (clntwf, pal#wf, commpm, clsswf, clsqwf, 
       srb#pm, dtcdpm, srd#pm) as (
    select
      substr(warpall.clntpm,1,2) as clntwf, 
      warpall.pal#pm as pal#wf, 
      warpall.commpm, 
      substr(warpall.clsspm,1,2) as clsswf, 
      warpall.clsqpm * 1 as clsqwf, 
      warpall.srb#pm, 
      warpall.dtcdpm, 
      warpall.srd#pm 
    from warpall
    where 
      warpall.locnpm <> 'ASSEMBLED PALLET'
      and warpall.commpm <> 'ASSEMBLED PALLET'
      and warpall.clsqpm <> 0
      and warpall.clntPM <> 'D2'
      and warpall.pal#pm = '1005609592'),

   alc (clntwf, pal#wf, commpm, clsswf, clsqwf, 
        srb#pm, dtcdpm, srd#pm) as (
     select 
       substr(warpalq.clntpq,1,2) as clntwf, 
       warpalq.pal#Pq as pal#wf, 
       pal.commpm, 
       substr(warpalq.clsspq,1,2) as clsswf, 
       warpalq.clsqpq * 1 as clsqwf, 
       '0', 
       '0', 
       pal.srd#pm 
     from warpalq
       join pal
         on waarpalq.pal#pq = pal.pal#wf
     where 
       warpalq.clsqpq <> 0
       and warpalq.clntPQ <> 'D2'
       and warpalq.pal#pq = '1005609592')

select 
  clntwf, commpm, fdsccd, clsqwf, pal#wf, dtcdpm, clsswf, srb#pm, descsc, cor#or  
from
  (select *
     from pal
   union all
   select *
     from alc
  ) as t9
  left outer join warcmdt as t3
    on t3.clntcd = t9.clntwf 
      and t3.commcd = t9.commpm
  left join warclss as t4
    on t4.clsssc = t9.clsswf
  left join warohrh as t5
    on t5.clntor = t9.clntwf 
      and t5.srn#or = t9.srd#pm
order by pal#wf asc

这使您可以在多个地方重复使用pal CTE，而无需重新定义它。这意味着您可以将其加入alc CTE 以获得commpm，该t9 稍后用于将t9 与warcmdt 一起加入。现在你不应该得到那个空值。我还将srd#pm 从warpall 带入alc CTE，因为它用于t9 和warohrh 之间的连接。如果这不正确，您可以在alc CTE 中将pal.srd#pm 替换为'0'。