strenght of relational model

Introduction The first database system is based on a network and layered model. A database can be defined as a collection of nonredundant data that can be shared by various application systems. A database means that the application separates the physical storage from the use of the data for program / data independence. In database systems, users, programmers, or application experts do not need to know the details of how the data is stored, and these details are usually "transparent" to the user.

In particular, most "relational" database systems support null values ​​and duplicate values. This by definition violates the true relational model. In the relational model, the table is a collection of tuples. Each tuple of each relationship contains the value of each attribute of the relationship. However, since null values ​​are not values, systems that allow null values ​​violate the relational model.

The most common database model in a general purpose database is a relational model, more precisely a SQL language. The process of creating a logical database design using this model uses a method approach called normalization. The purpose of normalization is to ensure that each basic "fact" is recorded in one place so that inserts, updates, and deletes can automatically maintain consistency. The final stage of database design is to make decisions that affect performance, scalability, recovery, security, etc., depending on the specific DBMS. This is often referred to as a physical database design and the output is a physical data model. The main goal at this stage is data independence. In other words, decisions aimed at optimizing performance do not appear to end users or applications. There are two types of data independent, physical data independent and logical data independent.

Database design: ER diagrams are used to model and design relational databases based on logical and business rules (in logical data models) and specific technologies implemented (within physical data models). In software engineering, the first step for determining the requirements of an information system project is ER diagram. It was later also used to model certain databases or databases. Relational databases have equivalent relational tables, which you can express as needed.