Question

我正试图与自己联系，但没有运气。

我的表包含：

ID    Name                         Position
1     Jefferson Roxas              president
2     Carlson Zafiro               president
3     Andrew Anderson              vice president
9     Jayson Dela Cruz             representative
10    Arille Villanueva Valdez     representative
11    Arnold Baltazar              representative

我想要的查询结果是：

ID   Name             Position     ID Name             Position        ID Name                      Position
1    Jefferson Roxas  president    3  Andrew Anderson  vice president  9  Jayson Dela Cruz          Representative
2    Carlson Zafiro   president                                        10 Arille Villanueva Valdez  Representative
                                                                       11 Arnold Baltazar           Representative

我正在使用此查询：

Select a.idcandidates, a.position, b.idcandidates, b.position , c.idcandidates, c.position
from tbl_candidates a, tbl_candidates b, tbl_candidates c
where a.position='president' and b.position='vice president' and c.position='representative'

但结果是

ID   Name             Position     ID Name             Position        ID Name                      Position
1    Jefferson Roxas  president    3  Andrew Anderson  vice president  9  Jayson Dela Cruz          Representative
2    Carlson Zafiro   president    3  Andrew Anderson  vice president  10 Arille Villanueva Valdez  Representative
1    Jefferson Roxas  president    3  Andrew Anderson  vice president  11 Arnold Baltazar           Representative
2    Carlson Zafiro   president    3  Andrew Anderson  vice president  9  Jayson Dela Cruz          Representative
1    Jefferson Roxas  president    3  Andrew Anderson  vice president  10 Arille Villanueva Valdez  Representative
2    Carlson Zafiro   president    3  Andrew Anderson  vice president  11 Arnold Baltazar           Representative

Answer 1

为什么不尝试使用三个单独的查询来执行UNION语句。例如。

Select Distinct a.idcandidates, a.position, b.idcandidates, b.position, c.idcandidates, c.position
from tbl_candidates a, tbl_candidates b, tbl_candidates c
where a.position='chairman'

UNION

Select Distinct a.idcandidates, a.position, b.idcandidates, b.position , c.idcandidates, c.position
from tbl_candidates a, tbl_candidates b, tbl_candidates c
where  and b.position='vice chairman'

UNION

Select Distinct a.idcandidates, a.position, b.idcandidates, b.position , c.idcandidates, c.position
from tbl_candidates a, tbl_candidates b, tbl_candidates c
where  c.position='representative'

我不知道这是否是您解决方案的替代方案。但是itws值得一试，看看你是否得到了你想要的结果。

Answer 2

每行需要一个parentID来表示层次结构，然后您的查询将更容易编写和动态。如果您提供表格，我可以提供答案

Answer 3

您想要的输出错过了关系查询的一些基本概念。我认为这几乎是其他答案在这里提到的。此外，您的查询与您提供的数据不一致。假设你真的是这个意思，

Select a.id, a.name, a.position, b.id, b.name, b.position , c.id, c.name, c.position
from tbl_candidates a, tbl_candidates b, tbl_candidates c
where a.position='president' and b.position='vice president' and c.position='representative'

然后，您所需的输出实际上只是这三个单独的查询恰好连接在它们的序数值上。如果是这种情况，那么让我们明确地这样做并将查询重新组合在一起。我不是MySQL的人，所以这就是我在SQL Server中的表现。

select 
  prs.id
  ,prs.name
  ,prs.position
  ,vcp.id
  ,vcp.name
  ,vcp.position
  ,rep.id
  ,rep.name
  ,rep.position
from (
    select 
      id
      ,name
      ,position
      ,row_number() over (order by id) rwn
    from 
      tbl_candidates
    where 
      position = 'president'
  ) prs 
  full outer join (
    select 
      id
      ,name
      ,position
      ,row_number() over (order by id) rwn
    from 
      tbl_candidates
    where 
      position = 'vice president'
  ) vcp on prs.rwn = vcp.rwn
  full outer join (
    select 
      id
      ,name
      ,position
      ,row_number() over (order by id) rwn
    from 
      tbl_candidates
    where 
      position = 'representative'
  ) rep on 
    rep.rwn = prs.rwn
    or rep.rwn = vcp.rwn

不幸的是，mysql没有row_number()。您可以尝试incorporate varables to build a row number instead。

这非常难看，所以我真的会考虑你的用例是什么，并试图改变它而不是这个解决方案。它确实提供了你想要的东西。

如何创建具有多个where的Join表

3 个答案: