11-15c# Foundation--The Paradigm Theory of database

The design theory and thinking of database

In the design of the database, there is a well-known design theory --- paradigm theory.

1. Content:

The first paradigm: the data types of each column should be unitary and must be unified;

The second paradigm: When designing the primary key, the primary key is as much as possible to reflect the data information in the table.

Example: Combined primary key in a fraction table

The number of goods and the time of the out of storage set the combined primary key

The third paradigm: each column in a table has data information that is directly related to the primary key as much as possible.

2, under what circumstances use ' paradigm theory '?

Take ' invoicing ' as an example:

Primary key design for foreign key table

Relationships between database tables:

Relationship to the primary foreign key table:1 relations to N , when this relationship occurs, it is drawn separately to design two tables.

When n - n relationships occur, the tables must be separate tables

11-15c# Foundation--The Paradigm Theory of database