In the vast majority of cases you should be able to have this information available at extract time. So you need to know if the record is a new one or was just modified. I have to admit it is not perfect, as this will only work if you can identify a changed record at source as either an Insert or an Update. The whole thing was wrecking my head a bit: how can we achieve the same thing in Oracle? Finally, I came up with a solution. Recently, this has also featured in Kimball's. If you are interested how exactly the Merge statement can be used in SQL Server 2008 to load an SCD2 have a look at this. As a result you have only one pass over the data, less logical I/O, and as a result improved performance. This extra functionality can be used to load a Slowly Changing Dimension Type 2 in one SQL statement. This new feature outputs merged rows for further processing, something which up until now (Oracle 11.1.0.7) is not possible in Oracle. The other day I came across a useful new feature in the Merge statement for SQL Server 2008. The download file is obtained directly from the publisher, not from any Peer to Peer file sharing applications such as Shareaza, Limewire, Kazaa, Imesh, eDonkey, eMule, Ares, BearShare, Overnet, Morpheus, BitTorrent Azureus and WinMX.
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