Running the script you will see the different results, because we use the DISTINCT clause inside the aggregate function SUM and it is allowed!
A Normalization Primer
For most DBAs, normalization is an understood concept, a bread and butter bit of knowledge. However, it is not at all unusual to review a database design by a development group for an OLTP (OnLine Transaction Processing) environment and find that the schema chosen is anything but properly normalized. This article by Brian Kelley will give you the core knowledge to data model.
2003-01-13
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