Three Forms
The first paradigm: no duplicate column
- The second paradigm: completely dependent on the primary key attribute
Third Pattern: transmitting attribute can not depend on other non-primary property
Paradigm role is to avoid data redundancy (duplicate data).
Paradigm question:
Paradigm designed in accordance with the table in data redundancy problem though is resolved, but it will generate many tables, leading to the complexity of the number of tables, and the second, query data, the time multi-table query is much higher than single-table queries time.
Anti paradigm
Paradigm purpose is to reduce data redundancy, and anti paradigm refers to allow a certain degree of data redundancy, the data object is to accelerate the operation.
Compared
Paradigm Paradigm is a contest and anti space and time to meet paradigm save space, speed up operations to meet the anti-paradigm.
Under the prerequisites are met paradigm of database design, and then complete the anti-paradigm design based on specific business needs.