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The idea is to structure data as much as possible to reduce data redundancy. In case you need to retrieve more than one object domain, then you must tie them together via joins. Denormalization over normalization means duplication of data and additional cost overhead on data storage side. The interior placement design of the brick & mortar retail store is usually done in such a way that customers can easily find the products they would like to purchase. If you were going to pick up 30 products at the retail store, it is very unlikely to find them all together already prepared for you at a classic retail store.