One common problem encountered with imported data is unexpected duplicate data rows, especially if the data is being consolidated from multiple sources. In previous versions of SQL Server, de-duping the data often involved the use of cursors and temp tables. Since the introduction of the
ROW_NUMBER ranking function and common table expressions in SQL Server 2005, you can de-dupe data with a single statement.
To demonstrate this approach, Listing 45.38 shows how to create an
authors_import table and populate it with some duplicate rows.
USE AdventureWorks2012GOCREATE TABLE dbo.authors_import( au_id char(11) ...