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Delete Duplicate Rows in SQL Server and Keep One Copy

To delete duplicate rows in SQL Server and keep one copy, number the rows in each group with ROW_NUMBER and delete every row after the first. This post finds the duplicates first, previews the rows that will go, and deletes them inside a transaction while saving a copy of what was removed. It ends with a unique index on a cleaned column, so the same address can’t come back.

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