database paradigm

1 normal form: the attribute is inseparable (corresponding to each column in the database that cannot be divided separately (it will be two columns if it is split, but this happens during design))
2 normal form: 1 normal form is satisfied, and non-main attributes are completely dependent For the main attribute (the main attribute--the attribute that appears in the candidate code)
3 normal form: satisfy the 2 normal form, and there is no transitive dependency (transitive dependence--A attribute determines the B attribute, and then determines the C attribute through the B attribute, then A determines C )
BC normal form: satisfy the 3 normal form, and there is no dependency between the main attributes