Question

我在SQL Server中有如下记录。

 Id    RefId    FromRefId 
  1     RH01    RH00 
  2     RH02    RH01 
  3     RH03    RH01 
  4     RH04    RH03
  5     RH05    RH02 
  6     RH06    RH03 
  7     RH07    RH04 
  8     RH08    RH02 
  9     RH09    RH05

我希望在条件

中使用Id获得如下结果

Where Id=1
RH02
RH03
RH04
RH05
RH06
RH07
RH08
RH09

Where Id=2
RH05
RH08
RH09

Where Id=3
RH04
RH06
RH07

Where Id=4
RH07

Where Id=5
RH09

谢谢，请指导我如何实现这一目标？

Answer 1

由于您希望获得FromRefId链之后的所有引用，因此需要使用递归查询，这可以使用recursive common table expression在SQL Server中实现：

with Recursive_IDs (Id, RefId, FromRefId) as (
  -- anchor query
  select Id, RefId, FromRefId
  from IDs

  union all

  -- recursive query
  select IDs.Id, IDs.RefID, Recursive_IDs.FromRefId
  from IDs
  inner join Recursive_IDs on Recursive_IDs.RefId=IDs.FromRefId
)
select Recursive_IDs.RefId
from Recursive_IDs
join IDs on Recursive_IDs.FromRefID=IDs.RefID
where IDs.id = [the id you want]

SQL fiddle

请注意，如果您不是按Id搜索，而是按RefId进行搜索，则可以稍微简化一下查询：

with Recursive_IDs (Id, RefId, FromRefId) as (
  -- anchor query
  select Id, RefId, FromRefId
  from IDs

  union all

  -- recursive query
  select IDs.Id, IDs.RefID, Recursive_IDs.FromRefId
  from IDs
  inner join Recursive_IDs on Recursive_IDs.RefId=IDs.FromRefId
)
select Recursive_IDs.RefId
from Recursive_IDs
where FromRefId = [the RefId you want]

Answer 2

您可以使用以下方法。我写了一个表值函数“GetChild”。它以递归方式遍历记录以获取所有依赖项，最后获取所有这些依赖项的RefId。


Create table hierarchy (Id int, RefId varchar(10), FromRefId varchar(10))
GO
insert into hierarchy
select   1,'RH01','RH00'  union all
select  2,'RH02','RH01'  union all
select  3,'RH03','RH01'  union all 
select  4,'RH04','RH03'  union all
select  5,'RH05','RH02'  union all 
select  6,'RH06','RH03'  union all 
select  7,'RH07','RH04'  union all 
select  8,'RH08','RH02'  union all 
select  9,'RH09','RH05'

GO
-- Table valued Function
GO
create function GetChild (@Id INT)
RETURNS @temp TABLE (RefId varchar(10))
AS
BEGIN

    declare @tempDependencies table (Id int)
    insert into @tempDependencies SELECT @Id

    WHILE ((Select COUNT(Id) from hierarchy where FromRefId in (select RefId from hierarchy where id in (select Id from @tempDependencies) ) and id not in (select Id from @tempDependencies)) > 0)
      BEGIN
      insert into @tempDependencies 
      Select Id from hierarchy where FromRefId in (select RefId from hierarchy where id in (select Id from @tempDependencies) ) and id not in (select Id from @tempDependencies)
      END

    insert into @temp 
    Select RefId from hierarchy where FromRefId in (select RefId from hierarchy where id in (SELECT Id from @tempDependencies))


    return 
END
GO


-- You may call the functions like this:

select * from GetChild(1)
select * from GetChild(2)
select * from GetChild(3)

SQL Fiddle Code

Answer 3

应该是一个简单的查询

SELECT * FROM your_table_name WHERE Id = your_desired_id

降级为什么？那不是你想要的吗？我认为你的问题不清楚。这里提到哪个ID？！

从SQL Server中选择记录，如下面的数据

3 个答案: