Second Normal Form (2NF)

Concepts covered: dmSecondNormalForm

2NF: No Partial Dependencies on Composite Keys 2NF only matters when your primary key spans multiple columns. If your PK is a single column, your table automatically satisfies 2NF. The violation: a non-key column depends on only PART of the composite key, not the whole thing. Consider a store inventory table with a composite PK of (store_id, product_id). The table includes store_name and product_name alongside the quantity. store_name depends only on store_id, not on the full key (store_id, product_id). product_name depends only on product_id. These are partial dependencies. The problem: 'Downtown' is stored once per product at that store. Add a third product and you have three copies of 'Downtown'. Rename the store and you must update every row. The fix: separate tables for stores and pro

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