Standardizing of database-relational schema

Armstrong Axiom

Reflexive law: X->y is y->x

Augmentation rate: A->d is AC->DC

Decomposition rate: A->BC is a->b,a->c

Dependency Relationship:

Trivial dependence: ab->b

Non-square dependent: ab->c

Partial dependence: Ab->d,b->d

Total dependence: No partial dependence is entirely dependent on

Paradigm

First paradigm: Each field can no longer be divided

Things you don't like can be divided again, not satisfying the requirements of the first paradigm.

After modification:

Second paradigm: Based on the first paradigm, the non-primary attribute is completely dependent on the primary attribute

The primary key is the build id+ vendor ID, the component id+ Vendor id-> Vendor name + vendor address, but the Supplier ID can determine the Supplier name + vendor address, so it does not meet the requirements of the second paradigm

After modification:

The third paradigm: based on the second paradigm, the non-primary attribute cannot be passed dependent on the primary attribute

Build number, manufacturer's name, component number, and manufacturer's address, but also manufacturer's name, the manufacturer's address, so there is a non-primary attribute transfer dependency on the main attribute, which does not conform to the third normal form requirement

After modification:

BC Paradigm: Based on the first paradigm, each non-trivial dependency must have a key code on the left side, and each determinant must contain a key code. Wikis: Any property, including non-primary and primary properties, cannot be determined by a non-primary property . (Personally feel better on the wiki)

property_id#->{county_name,lot#,area}; {County_name,lot#}->{property_id#,area}, but area->county_name, resulting in the dependency of other attribute properties on non-primary attributes, does not conform to BC paradigm requirements

After modification:

Standardizing of database-relational schema