Introduction to RDBMS

Key Concepts: Tables, Rows, Columns

Tables: In a relational database, a table is a collection of related data entries consisting of columns and rows. Each table has a unique name.

• Example: A table called Employees with columns EmployeeID, FirstName, LastName, and Department.

Rows: Also known as records or tuples, rows represent a single, implicitly structured data item in a table.

• Example: A row in the Employees table might be 1, John, Doe, HR.

Columns: Also known as attributes or fields, columns represent the structure of the table, where each column contains all the information of a single type (or attribute).

• Example: The FirstName column in the Employees table contains all employees' first names.

Primary Keys and Foreign Keys

Primary Key: A primary key is a column, or a set of columns, that uniquely identifies each row in a table. The primary key must contain unique values and cannot contain null values.

• Example: EmployeeID in the Employees table could be a primary key.

Foreign Key: A foreign key is a column, or a set of columns, that creates a link between two tables. It refers to the primary key of another table, ensuring referential integrity of the data.

• Example: If there is a Departments table with DepartmentID as the primary key, the Employees table can have a DepartmentID column as a foreign key referencing Departments(DepartmentID).