MySQL 8 Administrator???s Guide

Normalization

The data in the table columns must be kept non-redundant, considering the third normal form in the normalization theory. If the column holds repeating lengthy values, such as names or addresses, it is preferable to assign unique IDs and repeat these IDs across multiple smaller tables. In the event of searching, join queries should be used by referencing IDs in the join clauses.

In an application, if the preference is speed and not disk space or the maintenance costs of using multiple copies of data, it is advisable to duplicate the information or create summary tables to gain more speed. An example scenario could be a business intelligence system, where data is analyzed from large tables. In this case, normalization rules are ...