SQL Server ROW_NUMBER() Issue - sql

Question

I'm using row_number() expression but I don't get result as I expected. I have a sql table and some rows are duplicate. They have same 'BATCHID' and I want to get second row number for these, for others I use first row number. How can I do it?
SELECT * FROM (SELECT * , ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY) Rn FROM SAYIMDCPC ) t
WHERE Rn=1
This code returns to me only first rows, but I want to get second rows for duplicated items.

Answer 1

ROW_NUMBER() gives every row a unique counter. You'd want to use RANK(), which is similar, but gives rows with identical values the same score:
SELECT *
FROM (SELECT * , RANK() OVER (PARTITION BY batchid ORDER BY scaqry) rk
FROM sayimdcpc) t
WHERE rk = 1

Answer 2

If some values are only shown once, but some twice (and perhaps more than twice), you don't want the "first" row, you want the "max" row. Try reversing your order condition:
SELECT *
FROM (SELECT * ,
ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY DESC) Rn
FROM SAYIMDCPC ) t
WHERE Rn=1
As a side note, it's still better to explicitly list out all columns; for instance, you probably don't need Rn outside of this query...

Answer 3

Simply try this,
SELECT * FROM (SELECT * , ROW_NUMBER() OVER (ORDER BY SCAQTY) Rn FROM SAYIMDCPC ) t
WHERE Rn=1

Answer 4

To rephrase it another way, it sounds like you're saying, "When there's a single row for the Batch ID, return the single row. When there are 2 or more rows, return the second row." That's going to require inspecting your Rn value to see what its max is. I don't think you can do it in a single query.
So I'd try something like this:
WITH NumberedRows AS (
SELECT * ,
ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY) Rn
FROM SAYIMDCPC
)
, MaxNumber AS (
SELECT Max(RN) as MaxRn,
BATCHID
FROM NumberedRows
GROUP BY BATCHID
)
, NonDupes AS (
SELECT *
FROM NumberedRows
WHERE BATCHID NOT IN (SELECT BATCHID FROM MaxNumber WHERE MaxNumber = 1)
)
, SecondRows AS (
SELECT (
FROM NumberedRows
WHERE BATCHID NOT IN (SELECT BATCHID FROM MaxNumber WHERE MaxNumber > 1)
AND Rn = 2
)
SELECT
FROM NonDupes
UNION ALL
SELECT *
FROM SecondRows

Answer 5

Please try this. It will select max row num, if no duplicate then it should be first one otherwise second
select * from (SELECT * , ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY) Rn FROM SAYIMDCPC ) d,
(SELECT batchid,max(Rn) maxRn FROM (SELECT * , ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY) Rn FROM SAYIMDCPC ) t
group by batchid) q
where d.batchid = q.batchid and d.rn = q.maxrn

Answer 6

correct me if i am wrong
e.g sample data
BatchID, SCAQTY
1 , 10
2 , 10
2 , 20
2 , 30
is your expectation result like below?
**Expectation Result 1**
BatchID , SCAQty
1 , 10
2 , 30
or
**Expectation Result 2**
BatchID , SCAQty
1 , 10
2 , 20
2 , 30
based on my understanding what you want to perform is Expectation Result 1, so i guess Query below should able to help u, you just need to add desc for SCAQTY in your query
SELECT * FROM (SELECT * ,
ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY DESC) Rn FROM SAYIMDCPC ) t
WHERE Rn=1

Answer 7

Total result set with duplicates and non duplicates. The first column "IsDuplicate" indicates if the column is a duplicate or not.
;WITH d1 AS (
SELECT Seq = ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY)
,*
FROM SAYIMDCPC
)
SELECT IsDuplicate = CONVERT(BIT, Seq)
,*
FROM d1
This will give you only the duplicates:
;WITH d1 AS (
SELECT Seq = ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY)
,*
FROM SAYIMDCPC
)
SELECT IsDuplicate = CONVERT(BIT, Seq)
,*
FROM d1
WHERE Seq > 1
This will give you only the non duplicates (as in your first query)
;WITH d1 AS (
SELECT Seq = ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY)
,*
FROM SAYIMDCPC
)
SELECT IsDuplicate = CONVERT(BIT, Seq)
,*
FROM d1
WHERE Seq = 1