I've found that most of the time that developers want to denormalize it has nothing to do with performance. They just feel that storing the data in lots of places makes it easier for the task right in front of them because they don't have to do a join when they go retrieve the data. I have found that alot of developers have penchants for 'flag' columns. You can typically find the information by doing a join of a few tables, but that is too much trouble for the task right in front of them(they are not concerned about anything beyond that) so they want to create a flag.
There is a reason other than performance to have calculated fields. There are alot of crappy legacy databases, which require new development with tight time lines and no budget to change the existing model. In alot of these crappy models historical data is not tracked accurately so if you don't calculate the data at a specific point in time then you will never be able to correctly calculate it for that given time. Now I have also seen that you can get the correct data alot of the time, but the developers just don't know how and feel it's easier to just calculate it so they don't have to be bothered.
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Received on Tue Nov 01 2005 - 17:57:54 CST
