Data normalization is a fundamental process in modeling relational databases such as MySQL. This process involves organizing data into columns (attributes) and tables (relations) to minimize data redundancy and improve data integrity of the data. Normalization is performed through a series of rules called normal forms.
First normal form (1NF) is the most basic form of normalization. It requires that each column of a table contain only atomic values, that is, indivisible values. Also, each value in a column must be of the same data type. For example, if a column stores numbers, all values in that column must be numbers. This helps ensure data consistency.
Second normal form (2NF) is applied to tables that have a composite primary key, that is, a primary key consisting of more than one attribute. 2NF requires that each non-key attribute be functionally dependent on the entire primary key. This means that if an attribute can be determined by only part of the primary key, it must be moved to a different table.
Third normal form (3NF) goes one step further than 2NF by requiring all non-key attributes to be mutually independent. In other words, there should be no transitive dependencies, where one non-key attribute depends on another non-key attribute.
Fourth normal form (4NF) deals with multivalued dependencies. If a table has two or more independent attributes that are multivalued and dependent on the primary key, the table should be split into two or more tables to eliminate data redundancy.
Fifth normal form (5NF), also known as projection/junction, is the last commonly used normal form. It handles cases where a table can be split (split) into multiple tables and then recombined without data loss.
In MySQL, data normalization can be performed using a series of SQL commands. For example, to create a table in 1NF, you can use the CREATE TABLE command, specifying the table name and attributes with their respective data types. To move an attribute to a new table to satisfy 2NF or 3NF, you can use the ALTER TABLE command to remove the attribute from the original table and the INSERT INTO command to add the data to the new table. To split a table into multiple tables to satisfy 4NF or 5NF, you can use the CREATE TABLE command to create the new tables and the INSERT INTO command to populate the tables with data.
In summary, data normalization is a crucial part of database modeling in MySQL. It helps ensure data consistency and integrity by minimizing data redundancy and making data easier to maintain and query. While normalization can seem like a complex process, practice and understanding normal forms can make it second nature.
