Design paradigm of relational databases and database design paradigm

Design paradigm of relational databases and database design paradigm

1. 1NF)
The first paradigm is the basis of the second and third paradigm and the most basic paradigm. databases that do not meet the first paradigm are not relational databases.
Guiding principles of the first paradigm:
1) Each attribute of a Data Group can only contain one value.
2) Each array in the link must contain the same number of values.
3) Each array in the link must not be the same.

2. 2NF)
The second paradigm requires that the attributes of an object fully depend on the primary keyword, that is, there cannot be attributes that only depend on a part of the primary keyword,
If this attribute exists, this part of the primary keyword should be separated to form a new object. The new object and the original object are in a one-to-multiple relationship.

3. Third Paradigm (3NF)
The third paradigm requires that the relational table does not have a function dependency on any candidate keyword columns. That is to say, the third paradigm requires that a relational table does not contain non-primary keywords already contained in other tables.