1. The first normal form (1NF)
The first normal form (1NF) is the basic requirement for the relational model. A database that does not satisfy the first normal form (1NF) is not a relational database.
To satisfy atomicity
- No combined attributes
- Even if an attribute contains multiple information, it should be treated as a whole. For example, the student number 201805550101
contains the year of admission and professional class information, but it cannot be extracted from the student number. - Each tuple can only have one value on each attribute
2. Second Normal Form (2NF)
R is the first normal form, and each non-principal attribute is completely functionally dependent on the candidate code.
(Attributes not included in any candidate code are called non-primary attributes)
such as AB-> D, see if it can be B-> D or B-> D, if it can, then it is not 2NF
3. Third Normal Form (3NF)
R is the first normal form, and non-primary attributes cannot pass dependent candidate codes.
4. Boyce-Codd paradigm (BCNF)
R is the first normal form, and depends on a-> b for all functions of F, a is the supercode of R
