Employee Database

This project is a simple employee database management system created using SQL. It includes the creation of two tables: Departments and Employees, along with sample data and several SQL queries to retrieve information. The project is aimed at demonstrating how to set up a basic employee database and perform common operations.

Table of Contents

• Database Schema
• Sample Data
• SQL Queries
• EER Diagram

Database Schema

Departments

• DepartmentID (INT, Primary Key, Auto Increment) - Unique identifier for departments.
• DepartmentName (VARCHAR(50)) - Name of the department.

Employees

• EmployeeID (INT, Primary Key, Auto Increment) - Unique identifier for employees.
• FirstName (VARCHAR(50)) - First name of the employee.
• LastName (VARCHAR(50)) - Last name of the employee.
• DateOfBirth (DATE) - Date of birth of the employee.
• Gender (ENUM("Male", "Female")) - Gender of the employee.
• DepartmentID (INT, Foreign Key) - Department to which the employee belongs.
• Salary (DECIMAL(10, 2)) - Salary of the employee.
• HireDate (DATE) - Date when the employee was hired.

Sample Data

The Departments table contains various departments, and the Employees table includes sample employee records.

Departments Table

DepartmentID	DepartmentName
1	HR
2	Finance
3	Engineering
4	Sales
5	Marketing
6	IT
7	Operations
8	Customer Service
9	Research and Department
10	Legal
11	Quality Assurance

Employees Table

EmployeeID	FirstName	LastName	DateOfBirth	Gender	DepartmentID	Salary	HireDate
1	John	Smith	1980-05-15	Male	3	60000.00	2020-01-15
2	Sarah	Johnson	1990-07-20	Female	2	55000.00	2019-08-10
3	Michael	Williams	1985-02-10	Male	3	62000.00	2021-03-22
4	Emily	Brown	1992-11-30	Female	4	58000.00	2022-05-18
5	David	Jones	1988-09-05	Male	5	65000.00	2018-12-01
6	Olivia	Davis	1995-04-12	Female	2	54000.00	2023-02-10
7	James	Wilson	1983-03-25	Male	6	70000.00	2017-07-15
8	Sophia	Anderson	1991-08-17	Female	4	59000.00	2019-10-30
9	Liam	Miller	1979-12-01	Male	3	61000.00	2020-11-05
10	Emma	Taylor	1993-06-28	Female	5	63000.00	2022-04-02
11	Robert	Johnson	1982-09-14	Male	4	58000.00	2020-06-15
12	Mia	Moore	1987-03-03	Female	5	67000.00	2019-05-10
13	William	Clark	1984-04-20	Male	3	61000.00	2022-09-12
14	Charlotte	Anderson	1994-01-07	Female	2	55000.00	2019-11-28
15	Daniel	Davis	1989-08-25	Male	4	59000.00	2020-08-03
16	Sophia	Turner	1990-12-12	Female	5	64000.00	2018-10-15
17	Matthew	Parker	1986-06-08	Male	6	66000.00	2022-02-20
18	Ava	Williams	1993-03-15	Female	2	57000.00	2021-04-10

SQL Queries

The project includes various SQL queries for retrieving information from the database.

• To select all employees and departments:

  SELECT * FROM Employees;
  SELECT * FROM Departments;

• To find employees by department ID:

  SELECT * FROM Employees WHERE DepartmentID = 3;

• To find employees by department name (e.g., 'IT'):

  SELECT Employees.* FROM Employees
  INNER JOIN Departments ON Employees.DepartmentID = Departments.DepartmentID
  WHERE Departments.DepartmentName = 'IT';

• To select all data from employees and departments with department information:

  SELECT * FROM Employees
  LEFT JOIN Departments ON Employees.DepartmentID = Departments.DepartmentID;

• To select all data from employees and departments for a specific department (e.g., 'IT'):

  SELECT * FROM Employees
  LEFT JOIN Departments ON Employees.DepartmentID = Departments.DepartmentID
  WHERE Departments.DepartmentName = 'IT';

• To calculate the average salary of all employees:

  SELECT AVG(salary) FROM Employees;

EER-Diagram