Database pl-SQL [database standardization and paradigm]

Standardization is one of the secrets of IT database professionals. Data Modeling engineers, database administrators, and SQL developers must abide by this rule. We have long understood its principles and paradigms.

However, we have learned about most databases and found that they have implemented a third paradigm (3nf) at most ). Few databases execute higher paradigms, such as the Boyce-codd Paradigm (bcnf), the fourth paradigm (4nf), and the fifth Paradigm (5nf ). So why does most database designers not exceed 3nf?

Introduction to Paradigm

To answer these questions, it is important to understand the differences between 3nf, bcnf, 4nf, and 5nf. The following is an accurate definition of each paradigm.

1nf)

Each table must have a primary key, that is, the minimum set of attributes, which correspond to each record one by one. Delete duplicate groups by appropriately defining key and non-key attributes (different records seem to require different types of repeated data ). Note: Each attribute must contain a single value instead of a group of values.

2nf)

The database must meet all 1nf requirements. In addition, if a table has a composite key, all attributes must be associated with the entire key. In addition, redundant data between multiple rows in a table is moved to a separate table.

3nf)

The data stored in the table must not depend on any table field and must be unique in the primary key. The database must meet all 2nf requirements. Data that depends on both the primary key and other fields is moved to a separate table.

Boyce-coddParadigm (bcnf)

In addition to dependency on an attribute function for a candidate key Extension Set (called a super Key), there is no other non-trivial function dependency.

Fourth Paradigm (4nf)

Except for the dependency on an attribute group function for a candidate key extension set, there is no other non-trivial multi-value function dependency. If only one table conforms to bcnf and the multi-value dependency is function dependent, this table conforms to the fourth paradigm. 4nf deletes unnecessary data structures: multi-value dependencies.