Database Normalization: 2NF / 3NF / BCNF & Decomposition

Normal forms are a nested hierarchy 1NF ⊇ 2NF ⊇ 3NF ⊇ BCNF ⊇ 4NF that progressively removes redundancy by restricting which functional dependencies a schema may keep; classify a relation by first computing its candidate keys, then decompose losslessly (mandatory) and — where possible — dependency-preservingly (guaranteed only down to 3NF).