How do I get the record ID of the record with the

问题:

I have the following table

recordID               createdDate                         ForeignKeyID
00QA000000PtFXaMAN     2012-01-03 13:23:36.000             001A000000ngM21IAE
00QA000000OS2QiMAL     2011-12-15 12:03:02.000             001A000000ngM21IAE
.
.
.
.

I am trying to get the recordID for foreignKeyID where createdDAte is the min(createdDate) for foreignKeyID

if recordID is identity int I can get that by doing the following query

Select min(recordId),ForeignkeyID
from table 
group by ForeignKeyId

I originaly thought that I can create temp table with the following query and then joining it to table on minDate and foreignKeyID but then I found out that there are multiple records for foreignKeyId that has the same exact createdDate.

Select min(createdDate) as minDate,ForeignKeyID
from table
group by ForeignKeyId

I'm open with using temp table or subquery or anything really. Thanks.

回答1:

One of the ways to do it is

select A.ForeignKeyID, R.recordID
from (select distinct t.ForeignKeyID from table as t) as A
    outer apply
    (
        select top 1 t.recordID
        from table as t where t.ForeignKeyID = A.ForeignKeyID
        order by t.createdDate asc
    ) as R

SQL FIDDLE EXAMPLE

Another way to do it is

select top 1 with ties
    t.recordID, t.ForeignKeyID
from table as t
order by row_number() over (partition by t.ForeignKeyID order by t.createdDate)

SQL FIDDLE EXAMPLE

And another way

select A.recordID, A.ForeignKeyID
from
(
    select
        t.recordID, t.ForeignKeyID,
        row_number() over (partition by t.ForeignKeyID order by t.createdDate) as RowNum
    from table1 as t
) as A
where A.RowNum = 1

SQL FIDDLE EXAMPLE

I like second one more than others because of shortness of code

回答2:

SELECT 
    recordID, createdDate, ForeignKeyID
FROM
  ( SELECT 
        recordID, createdDate, ForeignKeyID,
        ROW_NUMBER() OVER ( PARTITION BY ForeignKeyID 
                            ORDER BY createdDate, recordID
                          ) AS rn
    FROM 
        tableX
  ) AS t
WHERE 
    rn = 1 ;