Q:  

What (if any) pros or cons come with creating summary tables in your data marts? An example would be to role up product revenue on a daily, weekly or monthly level.

A:  

Chuck Kelley’s Answer: The only question in my mind is why wouldn’t you create summary tables in data marts? The biggest pro for summary tables is faster response times (assuming that your end-user tool has some type of aggregate awareness). This also leads to the need for smaller sized CPUs and memory, since you do not need to read as many rows and do the aggregations each time someone does a query. The cons are it takes up more disk space and maintenance for the semantic layer since your end-user tool needs to have the semantic layer understand when the aggregate table can be used in place of the base table. Hopefully, the DBMS vendors will move this piece into the optimizers so it will not have to be in the semantic layers of all the products in the marketplace.

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