Database Fundamentals (Paradigm)

Database paradigm:

the construction database must follow certain rules. In a relational database, this rule is the paradigm.

       paradigm is a collection of relational patterns that conform to a certain level. Relationships in relational databases must meet certain requirements, that is, to meet different paradigms.

       the paradigm that satisfies the minimum requirements is the first paradigm. On the basis of the first paradigm, further satisfying more requirements is called the second paradigm, and the rest of the paradigms are based on the second analogy. In general, the database simply satisfies the third paradigm.

first normal form (1NF):

      in any relational database, the first paradigm (1NF) is the basic requirement for relational schemas, and a database that does not meet the first normal form (1NF) is not a relational database.  
      the so-called first normal form (1NF) means that each column of a database table is an indivisible basic data item. There cannot be more than one value in the same column, that is, an attribute in an entity cannot have multiple values or cannot have duplicate properties.

      the first paradigm is a column with no duplicates.

second normal form (2NF):

      the second paradigm is established on the basis of the first paradigm, that is, satisfying the second paradigm must first satisfy the first paradigm. The second paradigm requires that each instance or row in a database table must be divided by a unique region. It is often necessary to add a column to the table to store the unique identity of each instance.

      the second paradigm is that the non-principal attribute is dependent on the primary key.

third paradigm (3NF):

      satisfying the third paradigm must first satisfy the second paradigm. In short, the third paradigm requires that a database table not contain non-primary key information already contained in other tables.

The third paradigm is that attributes do not depend on other non-principal properties.

Database Fundamentals (Paradigm)