README.md

UNIVERSITY OF WEST ATTICA
SCHOOL OF ENGINEERING
DEPARTMENT OF COMPUTER ENGINEERING AND INFORMATICS

University of West Attica · Department of Computer Engineering and Informatics

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Databases I

Create and Manage a Database

Vasileios Evangelos Athanasiou
Student ID: 19390005

GitHub · LinkedIn

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Supervision

Supervisor: Periklis Andritsos, Professor

UNIWA Profile · LinkedIn

Co-supervisor: Anastasios Tsolakidis, Assistant Professor

UNIWA Profile · LinkedIn

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Athens, May 2023

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README

Create and Manage a Database

This documentation describes the database schema and SQL operations for managing departments, employees, projects, and assignments.

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Table of Contents

Section	Folder / File	Description
1	assign/	Assignment material
1.1	assign/assignment_01.pdf	Assignment description (English)
1.2	assign/εργασία_01.pdf	Assignment description (Greek)
2	docs/	Theoretical and practical documentation
2.1	docs/Create-Database.txt	Database creation guide (English)
2.2	docs/Δημιουργία-Βάσης-Δεδομένων.txt	Database creation guide (Greek)
3	Models/	Database schema diagrams
3.1	Models/model_01.png	Schema diagram 1
3.2	Models/model_02.png	Schema diagram 2
4	README.md	Project documentation
5	INSTALL.md	Usage instructions

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1. Database Structure

The database consists of four interconnected tables:

1.1 Departments (DEPT)

Stores information about company departments.

• Primary Key: DEPTNO
• Fields: DEPTNO, DNAME (Name), LOC (Location)

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1.2 Employees (EMP)

Maintains records for all personnel.

• Primary Key: EMPNO
• Foreign Key: DEPTNO (references DEPT)
• Fields: EMPNO, ENAME, JOB, HIREDATE, MGR (Manager ID), SAL (Salary), COMM (Commission), DEPTNO

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1.3 Projects (PROJ)

Lists specific projects within the organization.

• Primary Key: PROJ_CODE
• Fields: PROJ_CODE, DESCRIPTION

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1.4 Assignments (ASSIGN)

Junction table tracking employee project assignments.

• Primary Key: Composite Key (EMPNO, PROJ_CODE)
• Foreign Keys:
  • EMPNO (references EMP)
  • PROJ_CODE (references PROJ)
• Fields: EMPNO, PROJ_CODE, A_TIME (Assigned Time)

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2. Core SQL Operations

2.1 Data Definition (DDL)

Commands to create the database and table schemas:

CREATE DATABASE IF NOT EXISTS new_personnel;

CREATE TABLE DEPT (
    DEPTNO INT PRIMARY KEY,
    DNAME VARCHAR(50),
    LOC VARCHAR(50)
);

CREATE TABLE EMP (
    EMPNO INT PRIMARY KEY,
    ENAME VARCHAR(50),
    JOB VARCHAR(50),
    HIREDATE DATE,
    MGR INT,
    SAL DECIMAL(10,2),
    COMM DECIMAL(10,2),
    DEPTNO INT,
    FOREIGN KEY (DEPTNO) REFERENCES DEPT(DEPTNO)
);

CREATE TABLE PROJ (
    PROJ_CODE INT PRIMARY KEY,
    DESCRIPTION VARCHAR(100)
);

CREATE TABLE ASSIGN (
    EMPNO INT,
    PROJ_CODE INT,
    A_TIME INT,
    PRIMARY KEY (EMPNO, PROJ_CODE),
    FOREIGN KEY (EMPNO) REFERENCES EMP(EMPNO),
    FOREIGN KEY (PROJ_CODE) REFERENCES PROJ(PROJ_CODE)
);

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3. Data Manipulation (DML)

3.1 Sample data insertion:

INSERT INTO EMP VALUES (101, 'Codd', 'Analyst', '2020-01-10', NULL, 5000, NULL, 10);
INSERT INTO EMP VALUES (102, 'Elmasri', 'Analyst', '2020-02-15', NULL, 5200, NULL, 10);
INSERT INTO EMP VALUES (103, 'Navathe', 'Salesman', '2020-03-20', NULL, 4800, 200, 20);
INSERT INTO EMP VALUES (104, 'Date', 'Salesman', '2020-04-05', NULL, 4700, 150, 10);

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4. Verification

4.1 Check the schema and data:

DESCRIBE DEPT;       -- View table structure
DESCRIBE EMP;
DESCRIBE PROJ;
DESCRIBE ASSIGN;

SELECT * FROM DEPT;   -- View all records
SELECT * FROM EMP;
SELECT * FROM PROJ;
SELECT * FROM ASSIGN;