Understanding the Relational Database Model and Its Features

Relational Model: This approach allows users to obtain information from the database without assistance from information management professionals. The data is stored in a way that makes it easier for users to understand. The data is organized as tables, and the relationships between the rows and tables are visible in the data.

Features of Relational Models
It is important to know that the entries in the table are atomic. All entries in any column are of a single type. The table columns are called attributes. No two rows in the table are identical.

Structure of Relational Databases
The relational database model, at the conceptual level, is represented by a collection of stored relations.

Submodel Data
External schemas of relational sub-models are called relational data, each consisting of one or more scenarios (views) to describe the data required by a given application.

Storage Scheme
At the domestic level, each base table is implemented as a file stored on disk.

Data Sublanguage
This is a data management language for relational systems.

Formal Query Languages
In procedural languages, the user gives instructions to the system to perform a sequence of operations in the database to calculate the desired result. In non-procedural languages, the user describes the desired information without specifying a procedure for obtaining it.

Fundamental Operations
The operations select, project, and rename are called unit operations as they operate on a single table. The remaining operations operate on pairs of relations and are therefore called binary operations.

The Select Operation
This operation selects tuples (rows) that satisfy a given condition in a table. It is represented by the syntax:
(table_name WHERE condition);
The condition after the WHERE clause can include operators such as =, <, >, >=, <=.

The Project Operation
This operation identifies the columns (attributes in the ER model) that we are interested in. It is represented by brackets. If omitted, it indicates that we want to retrieve all columns of the table in question:
(table_name WHERE condition) [attr_name];

The Cartesian Product Operation
This operation multiplies all tuples between tables, resulting in a table that contains all columns from both tables. It is specified with the command:
table_name1 TIMES table_name2;

Join Operation
This operation obtains the product (multiplication) of all rows of one table with another, subsequently assessing those whose common field is generated as a result, creating a new table whose tuples (rows) meet the specified condition. It is represented by the syntax:
(table1) [attribute] JOIN (table2) [attribute];