How to select row with max value when duplicate rows exist in SQL Server

Question

I have table like this

DocumentID        | MasterStepID | StepNumber | RoleID | UserID     | Status
JIEP/TT/07/000174 | Approval1    |          1 |   NULL |         


        

Answer 1

Try This

SELECT T1.* FROM WF_Approval T1 
JOIN
(SELECT DISTINCT [Status], DocumentID, MAX(StepNumber) as [StepNumber] from WF_Approval 
GROUP BY DocumentID, [Status])  T2 
ON T1.DocumentID = T2.DocumentID AND T1.[Status] = T2.[Status]
AND T1.StepNumber = T2.StepNumber
ORDER BY StepNumber ASC, Status ASC

OUTPUT:

JIEP/TT/07/000174   Approval1   1   NULL    0006100022  1
JIEP/TT/07/000174   Approval1   5   18      0006100022  3
JIEP/TT/07/000174   Approval1   6   16      0006104115  6

Answer 2

The simple table (Student_Course) currently is like this with duplicate records assume:

Sname   Sid
------------
Ravi    S001
Ravi    S001
Jack    S002
Jack    S002
Jack    S002
Guru    S003
Smith   S004
Arun    S005
Rajeev  S006

Query:

SELECT S.Sid, S.Sname, Count(*) As Occurance
FROM Student_Course AS S
GROUP BY S.Sid
HAVING Count(S.Sid) > 1
Order By Count(*) Desc Limit 1

Output:

Sid     Sname   Occurance
-------------------------
S002    Jack    3

Answer 3

You're basically just missing a status comparison since you want one row per status;

SELECT *
FROM WF_Approval sr1
WHERE NOT EXISTS (
    SELECT *
    FROM  WF_Approval sr2 
    WHERE sr1.DocumentID = sr2.DocumentID AND 
          sr1.Status = sr2.Status AND                  # <-- new line
          sr1.StepNumber < sr2.StepNumber
) AND MasterStepID = 'Approval1'

or rewritten as a JOIN;

SELECT *
FROM WF_Approval sr1
LEFT JOIN WF_Approval sr2
  ON sr1.DocumentID = sr2.DocumentID 
 AND sr1.Status = sr2.Status
 AND sr1.StepNumber < sr2.StepNumber
WHERE sr2.DocumentID IS NULL
  AND sr1.MasterStepID = 'Approval1';

SQLfiddle with both versions of the query here.

Answer 4

This should be faster than a self-join because (most probably) only a single scan over the table is required.

select DocumentID, 
       MasterStepID, 
       StepNumber, 
       RoleID,
       UserID , 
       Status
from (
    select wf.*
           row_number() over (partition by wf.status order by wf.stepnumber desc) as rn
    from  WF_Approval wf
) t
where rn = 1
order by StepNumber