RELATIONAL SCHEMA

A relational schema in SQL is a description of a relational database. It consists of a set of relations, each of which is a table of data. Each relation has a name and a set of attributes, which are the columns in the table. The attributes can have different data types, such as integer, string, or date.

The relational schema also defines the primary key for each relation. The primary key is a unique identifier for each row in the table.

Here is an example of a relational schema for a database of employees in SQL:

CREATE TABLE Employees (

  employee_id INT NOT NULL,

  name VARCHAR(255) NOT NULL,

  department VARCHAR(255) NOT NULL,

  salary INT NOT NULL,

  PRIMARY KEY (employee_id)

);

This schema defines a table called Employees with four attributes: employee_id, name, department, and salary. The employee_id attribute is the primary key for the table.

Relational schemas are used to describe the structure of relational databases. They are a useful tool for database designers and developers.

Here are some additional things to keep in mind when creating a relational schema in SQL:

• The names of the relations should be descriptive and unique.
• The names of the attributes should be descriptive and consistent with the data type.
• The data types of the attributes should be appropriate for the data that they store.
• The primary key should be a unique identifier for each row in the table.