Question

我正在尝试编写查询，但我不确定我尝试做的是否正确。我解释这个的最好方法是向你展示我想要的和我拥有的东西

我想要的是什么：



   ID | SomeCol1 | SomeCol2 | Fish | Cat
   -------------------------------------
   1      foo        bar       baz   boz
   2      foo2       bar2      baz2  boz2

我有什么：

select
  tblA.id as "ID", 
  tblB.someCol as "SomeCol1",
  tblD.someOtherCol as "SomeCol2"
from TableA tblA
inner join TableB tblB on tblA.fkId1=tblB.id
inner join TableC tblC on tblA.id=tblC.fkId2
inner join TableD tblD on tblC.fkId8=tblD.id
inner join TableE tblE on tblC.fkId9=tblE.id

这正确地给了我前3列。

这个单独的查询为我提供了'Fish'

的正确列/值

select tblE.someCol as "Fish"
from TableA tblA
inner join TableB tblB on tblA.fkId1=tblB.id
inner join TableC tblC on tblA.id=tblC.fkId2
inner join TableD tblD on tblC.fkId8=tblD.id
inner join TableE tblE on tblC.fkId9=tblE.id
where tblD.someOtherColumn = 'Fish';

我会使用相同的表格为猫做一个类似的。

但是，如果我尝试通过嵌套选择来组合查询，那么我显然会得到“单行子查询返回超过1行”错误。

select
  tblA.id as "ID", 
  tblB.someCol as "SomeCol1",
  tblD.someOtherCol as "SomeCol2",
  (select tblE.someCol as "Fish"
    from TableA tblA
    inner join TableB tblB on tblA.fkId1=tblB.id
    inner join TableC tblC on tblA.id=tblC.fkId2
    inner join TableD tblD on tblC.fkId8=tblD.id
    inner join TableE tblE on tblC.fkId9=tblE.id
    where tblD.someOtherColumn = 'Fish'),
  (select tblE.someCol as "Cat"
    from TableA tblA
    inner join TableB tblB on tblA.fkId1=tblB.id
    inner join TableC tblC on tblA.id=tblC.fkId2
    inner join TableD tblD on tblC.fkId8=tblD.id
    inner join TableE tblE on tblC.fkId9=tblE.id
    where tblD.someOtherColumn = 'Cat')
from TableA tblA
inner join TableB tblB on tblA.fkId1=tblB.id
inner join TableC tblC on tblA.id=tblC.fkId2
inner join TableD tblD on tblC.fkId8=tblD.id
inner join TableE tblE on tblC.fkId9=tblE.id

那么，我怎么能正确地做到这一点？还有一种方法只引用一次表而不是多次，如上所示？ *我的真实世界查询更复杂，有更多的表可以加入，还有15个左右的列必须执行与'Fish'列相同的逻辑。

谢谢！

**更新 - 我想我已经明白了。我需要使用'with'命令创建一次子查询。然后我创建了子查询：


    with v_tbl as (
        select *
        from TableA tblA
        inner join TableB tblB on tblA.fkId1=tblB.id
        inner join TableC tblC on tblA.id=tblC.fkId2
        inner join TableD tblD on tblC.fkId8=tblD.id
        inner join TableE tblE on tblC.fkId9=tblE.id
    ), v_fish as (select name from v_tbl where tblD.someOtherColumn = 'Fish')
    , v_cat as (select name from v_tbl where tblD.someOtherColumn = 'Cat')
    select <regular query stuff>...

Answer 1

除非我遗漏了什么，否则我不明白为什么你需要一个子查询：

select
  tblA.id as "ID", 
  tblB.someCol as "SomeCol1",
  tblD.someOtherCol as "SomeCol2",
  tblE.someCol as "Fish"
from TableA tblA
inner join TableB tblB on tblA.fkId1=tblB.id
inner join TableC tblC on tblA.id=tblC.fkId2
inner join TableD tblD on tblC.fkId8=tblD.id
inner join TableE tblE on tblC.fkId9=tblE.id
where tblD.someOtherColumn = 'Fish';

Answer 2

我相信我已经解决了问题并在原帖中发布了答案

引用相同表的嵌套选择的正确Oracle语法是什么？

2 个答案: