Question

Ive got a table:

UserA UserB UserBB UserAA

for example:

1 2 2 1
1 3 3 1
2 1 1 2
2 4 4 2
2 5 5 2
5 2 2 5

What I want to achieve is to remove rows (duplicates) like to only leave rows as in example:

1 2 2 1
1 3 3 1
2 4 4 2
2 5 5 2



2 1 1 2 -> deleted because there is already 1 2 2 1 
5 2 2 5 -> deleted because there is already 2 5 5 2

How to write such a query ?

Thanks for help

Answer 1

— Find Duplicate Rows

SELECT  MAX(ID) as ID, CustName, Pincode FROM #Customers
GROUP BY CustName, Pincode
HAVING COUNT(*) > 1

— Delete Duplicate Rows

DELETE FROM #Customers
WHERE ID IN 
( SELECT    MAX(ID) FROM #Customers
GROUP BY CustName, Pincode
HAVING COUNT(*) > 1)

Taken from MSDN. :
http://archive.msdn.microsoft.com/SQLExamples/Wiki/View.aspx?title=DuplicateRows

Let me know if you are unable to figure it out from that code.

This may be a little bit closer to your needs. :

DELETE FROM TABLE
WHERE USERA IN ( SELECT MAX(USERA) FROM TABLE
GROUP BY USERA, USERB, USERBB, USERAA HAVING COUNT(*) > 1)