How to find duplicate values in SQL Server

Posted by hgulyan on Stack Overflow See other posts from Stack Overflow or by hgulyan
Published on 2010-05-20T09:30:15Z Indexed on 2010/05/20 10:50 UTC
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sql-server-2008

Hi,

I'm using SQL Server 2008. I have a table

Customers

customer_number int

field1 varchar

field2 varchar

field3 varchar

field4 varchar

... and a lot more columns, that doesn't matter for my queries.

Column *customer_number* is pk. I'm trying to find duplicate values and some differences between them.

Please, help me to find all rows that have same

1) field1, field2, field3, field4

2) only 3 columns are equal and one of them isn't (except rows from list 1)

3) only 2 columns equal and two of them aren't (except rows from list 1 and list 2)

In the end, I'll have 3 tables with this results and additional groupId, which will be same for a group of similars (For example, for 3 column equals, rows that have 3 same columns equal will be a seperate group)

Thank you.

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