5

我想知道是否有人遇到过这个问题的巧妙解决方案。我正在尝试从几个表中选择数据，让记录逐行匹配。我基本上是在完全外部连接之后，但有一个关键的区别。如果我在一个表中要加入的列中有四行具有特定值，而在另一个表中具有该值的三行，我只希望将前三个结果连接起来，第四个结果就好像有没有匹配。

这样做的原因是创建一个对账报告，以确保在比较结果时不会多次计算交易。我可以通过使用一些分组和一些聚合函数来解决这个问题，但这隐藏了一些我想保留的细节。

下面是一个显示我所追求的东西的示例，评论中的无效/伪代码说明了我如何认为这是有效的：

declare @t1 table (id bigint identity(1,1) primary key clustered, foreignKeyId bigint, otherData nvarchar(10))
declare @t2 table (id bigint identity(1,1) primary key clustered, foreignKeyId bigint, moreData nvarchar(10))

insert @t1 select 1, '1.1.1'
 union all select 1, '1.1.2'
 union all select 1, '1.1.3'
 union all select 3, '1.3.1'
 union all select 3, '1.3.2'
 union all select 3, '1.3.3'
 union all select 4, '1.4.3'

insert @t2 select 1, '2.1.1'
 union all select 1, '2.1.2'
 union all select 1, '2.1.3'
 union all select 2, '2.2.1'
 union all select 3, '2.3.1'
 union all select 3, '2.3.2'
 union all select 5, '2.5.1'
 union all select 5, '2.5.2'

--demo of the functionality i'm hoping to acheive 
--
 /*
 select t1.id           id1
 , t2.id                id2
 , t1.foreignKeyId  fk1
 , t2.foreignKeyId  fk2
 , t1.otherData     otherData
 , t2.moreData      moreData
 from @t1 t1
 full funky join @t2 t2
 on t1.foreignKeyId = t2.foreignKeyId
 order by t1.id, t2.id --we'd need an order by to ensure the match could be applied in a predictable manner
 */
--
declare @funkyjoin table (id1 bigint, id2 bigint, fk1 bigint, fk2 bigint, otherData nvarchar(10), moreData nvarchar(10))
declare @id1 bigint, @id2 bigint
insert @funkyjoin (id1, fk1, otherData) 
select id, foreignKeyId, otherData from @t1

while exists(select 1 from @t2)
begin
    select top 1 @id2 = id from @t2 order by id 

    set @id1 = null

    select top 1 @id1 = id1 
    from @funkyjoin
    where fk2 is null
    and fk1 in (select foreignKeyId from @t2 where id = @id2)

    if @id1 is null
    begin
        insert @funkyjoin (id2, fk2, moreData)
        select id, foreignKeyId, moreData
        from @t2
        where id = @id2
    end
    else
    begin
        update @funkyjoin
        set id2 = @id2
        , fk2 = fk1 --since we're joining on this we can just match it
        , moreData = (select moreData from @t2 where id = @id2)
        where id1 = @id1 
    end

    delete from @t2 where id = @id2 --since this is only an example let's not worry about keeping our source data
end

select * 
from @funkyjoin
order by coalesce(id1, id2)

我已经为以前在电子表格上发生这种情况时编写了一个类似的解决方案：http: //officemacros.codeplex.com/#WorksheetMergeMacro

4

2 回答 2

5

如果我理解正确，这可能是你所追求的：

select *
from (
  select *,
    row_number() over (partition by foreignKeyId order by id) as n
  from @t1
) t1
full outer join (
  select *,
    row_number() over (partition by foreignKeyId order by id) as n
  from @t2
) t2 on t1.foreignKeyId = t2.foreignKeyId and t1.n = t2.n
于 2012-06-06T15:24:33.310 回答
1

用完行的最佳方法是添加一个伪行号（使用 ROW_NUMBER）并将其包含在连接中。

于 2012-06-06T15:21:48.743 回答