data structure complexity vs. application maintenance cost

I hope I can express my question..:
I need to confront, how data structure complexity implies the cost of
coding/maintenance application based on it.

It's because I need to argue my principal, he need to focus more on database
structure _before we start coding functionalities. Because of deadlines,
there is a suggesion, we can simplify database structers after we start
writting application. I suggest there is numerously more mony to do so.

Any articels, charts, or expert statemets on subject? :)



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