SQL JOIN

An SQL JOIN is used to combine data from related tables.
Example: If you have two tables. Employee and Department, and you want to see a combined view of Employee data and Department data, you can use SQL JOINs.
Imagine that we have two tables, Employee and Department as given below.

Employee Table

Rambo

Robert

Mugambo

Satraj

Nagashekar

Rao

Tom

Harry

Dana

Laura

Rambo

Fox

Giselle

Chivvi

Consider the following Department table:

Department Table

Engineering

Management

Finance

Kitchen

Scenario: Get Employee First Name, Last Name and Department Name.
For the above scenario, we can join the two tables using the JOIN clause.

SELECT EMPLOYEE.FIRSTNAME, EMPLOYEE.LASTNAME, DEPARTMENT.DEPARTMENTNAME
	FROM EMPLOYEE, DEPARTMENT 
	WHERE EMPLOYEE.DEPARTMENTID = DEPARTMENT.DEPARTMENTID

Result:

Rambo

Robert

Engineering

Mugambo

Satraj

Engineering

Nagashekar

Rao

Management

Tom

Harry

Management

Dana

Laura

Kitchen

Rambo

Fox

Kitchen

Giselle

Chivvi

Finance

In the above SELECT Query, we joined two tables, Employee and Department based on foreign key, DEPARTMENTID.
By doing that, we are successfully able to show the department name also in the result.