Explain the principle of data normalization in an SQL database and why it is necessary.

Data normalization is the process of organizing data in a database to reduce redundancy and improve data integrity. It involves splitting tables into smaller ones and establishing relationships between them.

The main goals of normalization:

• Eliminating data duplication, which saves space and simplifies updates.
• Ensuring data integrity so that changes in one place are correctly reflected throughout the database.
• Simplifying the database structure for more efficient management and queries.

For example, instead of storing information about clients and their orders in one table, the data is split into two tables: "Clients" and "Orders," linked by the client key.