Tom.Thomson (6/13/2011)

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Good question.

But one major niggle and one minor niggle:

Major niggle: if page compression is enabled on a table already containing data, each page is rebuilt and evaluated for page compression; page compression can occur here (unless I've got it wrong) and may make the data fit into fewer pages than if only row compression occurred. So the answer always applies to pages which are empty/unallocated when compression is enabled, but not always to pages which already contain data when compression is enabled.

Minor niggle: page compression won't occur even when a new row doesn't fit if the engine determines that page compression would not free up a significant amount of space.

edit: SCTEs