Auto Shop Database

In the following example - Database for an auto shop business, we have a list of departments, employees, customers and customer cars. We are using foreign keys to create relationships between the various tables.

Relationships between tables

• Each Department may have 0 or more Employees
• Each Employee may have 0 or 1 Manager
• Each Customer may have 0 or more Cars

Departments

Id Name

1 HR
2 Sales
3 Tech

SQL statements to create the table:

CREATE TABLE Departments (
Id INT NOT NULL AUTO_INCREMENT,
Name VARCHAR(25) NOT NULL,
PRIMARY KEY(Id)
);

INSERT INTO Departments
([Id], [Name])
VALUES
(1, 'HR'),
(2, 'Sales'),
(3, 'Tech')
;
Employees

Id FName LName PhoneNumber ManagerId DepartmentId Salary HireDate

1 James Smith 1234567890 NULL 1 1000 01-01-2002
2 John Johnson 2468101214 1 1 400 23-03-2005
3 Michael Williams 1357911131 1 2 600 12-05-2009
4 Johnathon Smith 1212121212 2 1 500 24-07-2016

SQL statements to create the table:

CREATE TABLE Employees (
Id INT NOT NULL AUTO_INCREMENT,
FName VARCHAR(35) NOT NULL,
LName VARCHAR(35) NOT NULL,
PhoneNumber VARCHAR(11),
ManagerId INT,
DepartmentId INT NOT NULL,
Salary INT NOT NULL,
HireDate DATETIME NOT NULL,
PRIMARY KEY(Id),
FOREIGN KEY (ManagerId) REFERENCES Employees(Id),
FOREIGN KEY (DepartmentId) REFERENCES Departments(Id)
);

INSERT INTO Employees
([Id], [FName], [LName], [PhoneNumber], [ManagerId], [DepartmentId], [Salary], [HireDate])
VALUES
(1, 'James', 'Smith', 1234567890, NULL, 1, 1000, '01-01-2002'),
(2, 'John', 'Johnson', 2468101214, '1', 1, 400, '23-03-2005'),
(3, 'Michael', 'Williams', 1357911131, '1', 2, 600, '12-05-2009'),
(4, 'Johnathon', 'Smith', 1212121212, '2', 1, 500, '24-07-2016');

Customers

Id FName LName Email PhoneNumber PreferredContact

1 William Jones [email protected] 3347927472 PHONE
2 David Miller [email protected] 2137921892 EMAIL
3 Richard Davis [email protected] NULL EMAIL

SQL statements to create the table:

CREATE TABLE Customers (
Id INT NOT NULL AUTO_INCREMENT,
FName VARCHAR(35) NOT NULL,
LName VARCHAR(35) NOT NULL,
Email varchar(100) NOT NULL,
PhoneNumber VARCHAR(11),
PreferredContact VARCHAR(5) NOT NULL,
PRIMARY KEY(Id)
);

INSERT INTO Customers
([Id], [FName], [LName], [Email], [PhoneNumber], [PreferredContact])
VALUES
(1, 'William', 'Jones', '[email protected]', '3347927472', 'PHONE'),
(2, 'David', 'Miller', '[email protected]', '2137921892', 'EMAIL'),
(3, 'Richard', 'Davis', '[email protected]', NULL, 'EMAIL') ;

Cars

Id CustomerId EmployeeId Model Status Total Cost
1 1 2 Ford F-150 READY 230
2 1 2 Ford F-150 READY 200
3 2 1 Ford Mustang WAITING 100
4 3 3 Toyota Prius WORKING 1254

SQL statements to create the table:

CREATE TABLE Cars (
Id INT NOT NULL AUTO_INCREMENT,
CustomerId INT NOT NULL,
EmployeeId INT NOT NULL,
Model varchar(50) NOT NULL,
Status varchar(25) NOT NULL,
TotalCost INT NOT NULL,
PRIMARY KEY(Id),
FOREIGN KEY (CustomerId) REFERENCES Customers(Id),
FOREIGN KEY (EmployeeId) REFERENCES Employees(Id)
);

INSERT INTO Cars
([Id], [CustomerId], [EmployeeId], [Model], [Status], [TotalCost])
VALUES
('1', '1', '2', 'Ford F-150', 'READY', '230'),
('2', '1', '2', 'Ford F-150', 'READY', '200'),
('3', '2', '1', 'Ford Mustang', 'WAITING', '100'),
('4', '3', '3', 'Toyota Prius', 'WORKING', '1254') ;

Library Database

In this example database for a library, we have Authors, Books and BooksAuthors tables.

Authors and Books are known as base tables, since they contain column definition and data for the actual entities in the relational model. BooksAuthors is known as the relationship table, since this table defines the relationship between the Books and Authors table.

Relationships between tables

• Each author can have 1 or more books
• Each book can have 1 or more authors

Authors

(view table)

Id Name Country
1 J.D. Salinger USA
2 F. Scott. Fitzgerald USA
3 Jane Austen UK
4 Scott Hanselman USA
5 Jason N. Gaylord USA
6 Pranav Rastogi India
7 Todd Miranda USA
8 Christian Wenz USA

SQL to create the table:

CREATE TABLE Authors (
Id INT NOT NULL AUTO_INCREMENT,
Name VARCHAR(70) NOT NULL,
Country VARCHAR(100) NOT NULL,
PRIMARY KEY(Id)
);

INSERT INTO Authors('J.D. Salinger', 'USA'),
('F. Scott. Fitzgerald', 'USA'),
('Jane Austen', 'UK'),
('Scott Hanselman', 'USA'),
('Jason N. Gaylord', 'USA'),
('Pranav Rastogi', 'India'),
('Todd Miranda', 'USA'),
('Christian Wenz', 'USA') ;

Books

(view table)

Id Title
1 The Catcher in the Rye
2 Nine Stories
3 Franny and Zooey
4 The Great Gatsby
5 Tender id the Night
6 Pride and Prejudice
7 Professional ASP.NET 4.5 in C# and VB

SQL to create the table:

CREATE TABLE Books (
Id INT NOT NULL AUTO_INCREMENT,
Title VARCHAR(50) NOT NULL,
PRIMARY KEY(Id)
);

INSERT INTO Books
(Id, Title)
VALUES
(1, 'The Catcher in the Rye'),
(2, 'Nine Stories'),
(3, 'Franny and Zooey'),
(4, 'The Great Gatsby'),
(5, 'Tender id the Night'),
(6, 'Pride and Prejudice'),
(7, 'Professional ASP.NET 4.5 in C# and VB') ;

BooksAuthors

(view table)

BookId AuthorId
1 1
2 1
3 1
4 2
5 2
6 3
7 4
7 5
7 6
7 7
7 8

SQL to create the table:

CREATE TABLE BooksAuthors (
AuthorId INT NOT NULL,
BookId INT NOT NULL,
FOREIGN KEY (AuthorId) REFERENCES Authors(Id),
FOREIGN KEY (BookId) REFERENCES Books(Id)
);

INSERT INTO BooksAuthors
(BookId, AuthorId)
VALUES
(1, 1),
(2, 1),
(3, 1),
(4, 2),
(5, 2),
(6, 3),
(7, 4),
(7, 5),
(7, 6),
(7, 7),
(7, 8) ;

Examples

View all authors (view live example):

SELECT * FROM Authors;
View all book titles (view live example):

SELECT * FROM Books;
View all books and their authors (view live example):

SELECT
ba.AuthorId,
a.Name AuthorName,
ba.BookId,
b.Title BookTitle
FROM BooksAuthors ba
INNER JOIN Authors a ON a.id = ba.authorid
INNER JOIN Books b ON b.id = ba.bookid

Countries Table

In this example, we have a Countries table. A table for countries has many uses, especially in Financial applications involving currencies and exchange rates.

Live example: SQL fiddle
Some Market data software applications like Bloomberg and Reuters require you to give their API either a 2 or 3 character country code along with the currency code. Hence this example table has both the 2-character ISO code column and the 3 character ISO3 code columns.

Countries

(view table)

Id ISO ISO3 ISONumeric CountryName Capital ContinentCode CurrencyCode

1 AU AUS 36 Australia Canberra OC AUD
2 DE DEU 276 Germany Berlin EU EUR
2 IN IND 356 India New Delhi AS INR
3 LA LAO 418 Laos Vientiane AS LAK
4 US USA 840 United States Washington NA USD
5 ZW ZWE 716 Zimbabwe Harare AF ZWL

SQL to create the table:

CREATE TABLE Countries (
Id INT NOT NULL AUTO_INCREMENT,
ISO VARCHAR(2) NOT NULL,
ISO3 VARCHAR(3) NOT NULL,
ISONumeric INT NOT NULL,
CountryName VARCHAR(64) NOT NULL,
Capital VARCHAR(64) NOT NULL,
ContinentCode VARCHAR(2) NOT NULL,
CurrencyCode VARCHAR(3) NOT NULL,
PRIMARY KEY(Id)
) ;

INSERT INTO Countries
(ISO, ISO3, ISONumeric, CountryName, Capital, ContinentCode, CurrencyCode)
VALUES
('AU', 'AUS', 36, 'Australia', 'Canberra', 'OC', 'AUD'),
('DE', 'DEU', 276, 'Germany', 'Berlin', 'EU', 'EUR'),
('IN', 'IND', 356, 'India', 'New Delhi', 'AS', 'INR'),
('LA', 'LAO', 418, 'Laos', 'Vientiane', 'AS', 'LAK'),
('US', 'USA', 840, 'United States', 'Washington', 'NA', 'USD'),
('ZW', 'ZWE', 716, 'Zimbabwe', 'Harare', 'AF', 'ZWL')