Shulou(Shulou.com)06/01 Report--

The design of relational database follows six paradigms: the first paradigm (1NF), the second paradigm (2NF), the third paradigm (3NF), the Buss-Cod paradigm (BCNF), the fourth paradigm (4NF) and the fifth paradigm (5NF). First normal form 1NF

1NF, that is, each data column of a database table is an indivisible atomic data item.

Second normal form 2NF

2NF requires that non-code attributes must be completely dependent on candidate codes on the basis of 1NF. That is, there must be a primary key field that uniquely identifies a row of data.

The third normal form 3NF

3NF requires that on the basis of satisfying 2NF, any non-primary attribute does not depend on other non-primary attributes. That is, redundant fields are not allowed. For example, there is a department information table in which each department has a department number (dept_id), department name, department profile, and so on. Then after the department number is listed in the employee information table, the department name, department profile and other department-related information can no longer be added to the employee information table.

Pascod normal form BCNF

BCNF requires that on the basis of satisfying 3NF, any non-primary attribute can not be dependent on the primary key subset.

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