MySQL Normalization-Pre-launch-co-development

First paradigm: A field in a database table is a single attribute and cannot be divided.

One sentence summary: As long as the relational database is satisfied with the first paradigm.

Second paradigm: Entity's attributes are completely dependent on the primary keyword

Example: multiple patients correspond to a doctor. Split the Doctor's watch.

Non-keyword fields are dependent on the primary key, but such splits do not conform to the third paradigm.

The third paradigm: is a subset of the second paradigm, that satisfies the third paradigm must satisfy the second paradigm.

a non-critical field that does not exist is dependent on the transfer function of either of the candidate key fields.

Example: The department name depends on the department number, the department number depends on the doctor number, there is redundancy here, so does not conform to the third paradigm.

Summary: When developing an application, the database is designed to adhere to the three paradigms to the greatest extent, especially for OLTP type System. The three paradigms are the rules that must be observed. The biggest problem with the three paradigms is that many tables are often required for queries, and queries are inefficient.

Performance Considerations - do redundancy -- achieve the goal of improving efficiency. --- inverse normalization

This article from the "Clear Sky" blog, declined reprint!

MySQL Normalization-Pre-launch-co-development