SQL Server query distinct

Question

I'm trying to do a query in SQL Server 2008. This is the structure of my table

Recno     ClientNo      ServiceNo
---------------------------------
1234      17            27
2345      19            34
3456      20            33
4567      17            34

I'm trying to select RecNo however, filtering by distinct ClientNo , so for some clients such as client no 17 - they have more than 1 entry, I'm trying to count that client only once. So basically, looking at this table, I'm only supposed to see 3 RecNo's, since there are only 3 distinct clients. Please help

Select RecNo, Count(ClientNo)
from TblA
where Count(clientNo)<2

Something like this?

EDIT:

The value of RecNo is not relevant, I only need to have an accurate number of records. In this case, I'd like to have 3 records.

Answer 1

oaky you are getting some crazy answers probably becuase your desired result is not clear so I suggest if some of these are not what you need that you clarify your desired result.

If you want the answer 3, I can only assume you want a count of DISTINCT ClientNo's if so it is simply aggregation.

SELECT COUNT(DISTINCT ClientNo) as ClientNoDistinctCount
FROM
    TblA
GROUP BY
    ClientNo

Answer 2

Ok, this will give you the count that you want:

WITH CTE AS
(
    SELECT  *,
            RN = ROW_NUMBER() OVER(PARTITION BY ClientNo ORDER BY Recno)
    FROM TblA
)
SELECT COUNT(DISTINCT Recno) N
FROM CTE
WHERE RN = 1;

Answer 3

Try this..

   ;with cte1
  As(SELECT Recno,clientno 
  ,row_number() over(partition by clientno order by Recno )RNO FROM TblA)
   Select Recno,clientno 
   From cre1 where RNO=1

Answer 4

Choose only ClientNo having the max Recno (or replace < with > to choose the min one).

Select *
from TblA t1
where not exists(select 1 
         from TblA t2
         where t1.ClientNo = t2.ClientNo and t1.Recno < t2.Recno )  

BTW, the other solution already mentioned, utilizing row_number() needs no CTE in this case

SELECT TOP(1) WITH TIES *
FROM TblA
ORDER BY ROW_NUMBER() OVER(PARTITION BY ClientNo ORDER BY Recno)