Database Relationships

Let this course take you from knowing nothing about databases all the way to structuring tables like a professional!

Created byCaleb Curry

Last updated 4/2015

English

What you'll learn

Create correct Database Relationships
Design databases with referential integrity
Design primary keys and foreign keys
Use gained skills to correct bad designs in database structures
Decide which tables should be parents and which tables should be children

Course content

6 sections • 22 lectures • 1h 43m total length

Introduction0:50
Welcome to this course! It will be an introductory course to database concepts! Don't expect to be a master after this course. On the bright side though, this course will have a lot of useful content!

Entities and Attributes3:16
Entities are what we store Data about, Attributes are the things we store about the entity.
Every type of entity in a database will have its own table. Each attribute about that entity will have its own column.
Relations5:31
Relations are tables. This comes from algebra, but we don't need to worry too much about that for beginning database design.
Data Integrity4:46
It is important to have data integrity within our database. Data integrity is protecting the structure of our database and keeping our data up-to-date and accurate.
Atomicity1:24
When things are atomic they only contain one thing. They can no longer be broken up into smaller groups of data.
In our database we want our tables, columns, and data to be atomic.
Primary and Foreign Keys4:25
What is a Relationship?3:02
A relationship is when we have a foreign key in one table that references a primary key in another table.

Keep in mind that a relational database management system is not called relational because it has relationships, it's called relational because tables are known as relations (see previous video).

Conceptual Vs. Physical Relationships2:13
There is a difference between conceptual and physical relationship design.

When we design conceptually, we are thinking of how the entities are related in real world situations.
When we design physically, we are thinking of how we take that real world relationship and turn it into tables with primary keys and foreign keys.
One-to-One Relationships (Conceptual)3:28
A one-to-one relationship exists when an entity is in an exclusive relationship with one other entity. No other entities allowed.

The example given was of a marriage where the husband and wife were not allowed to marry anybody else.
One-to-Many Relationships (Conceptual)4:27
A one-to-many relationship exists when an entity can be in a relationship with multiple other entities but each of the other entities can only be in a relationship with the original entity exclusively.

The example I gave was a jelous king we marries unlimited wives but each wife was to only be in a relationship with that king.
Many-to Many-Relationships (Conceptual)2:40
A many-to-many relationship exists when any number of entities have relationships with any number of entities. There is no limit.

There is no practical way to store this in a database so we'll learn a trick in future videos.
Sometimes You Decide on the Relationship2:39
Sometimes you will have to decide the relationship.

Relationships are not always set in stone. You must decide the best way to design a database. This could either be by your own intellect or rules given to you by a boss or team leader. These rules are called business rules.

Referential Integrity9:51
Referential integrity goes hand in hand with data integrity. In fact, referential integrity is only one kind of data integrity. There are many more types!
Parent and Child Tables5:13
Whenever you have a foreign key referencing a primary key you will have a parent table and a child table. The primary key is the parent and the foreign key is the child.
NOT NULL5:46
NOT NULL is a column characteristic that prevents that column from being left empty.

How to Structure One-to-One Relationships9:03
To model one-to-one relationships we have two tables where one is given the foreign key that references the other table. It usually will not matter which one you put the foreign key in because the relationship is exclusive.
One-to-One Examples6:06
If you are struggling to understand these examples, watch the previous video or do some extra research.
How to Structure One-to-Many Relationships8:13
To model one-to-many relationships we will give a foreign key to each row in the child table that references the parent. We will not put any information about the child in the parent table.
One-To-Many Examples6:17
If you are struggling to understand these examples, watch the previous video or do some extra research.
How to Structure Many-to-Many Relationships6:07
To structure many-to-many relationships we need to break the relationship up into 2 one-to-many relationships. This means that we will have a total of 3 tables, 2 parents and 1 child (the intermediary table).

Each connection between the two parents within the intermediary table will be the primary key. So they will have to be unique.
Many-to-Many Examples7:07
If you are struggling to understand these examples, watch the previous video or do some extra research.
Think you can structure relationships?

Requirements

A notepad and pencil for drawing out database designs and taking notes

Description

The hardest part about databases is that there is a huge mountain of knowledge needed before even beginning to understand how to design and create them. It doesn't have to be this way. This course will take you from knowing nothing about databases to being able to decisively design relationships between tables. Now, if you're a beginner, you might be asking..."What are database relationships and why do they matter?" The answer is simple, every database is built off the fundamentals of database relationships.

If you want to really understand what a database is, how it works, and how to design your very first set of database tables, this course is for you.

Every lecture is taught in an easy to follow method using on-screen illustrations, drawings, and examples. This course will bring you to a level of understanding that will allow you to develop skills quickly and use them at home, in school, and even in the work setting. These are practical skills. The skills learned in this course are skills that can help you get a job in IT or Database design.

Do you want even better news? These skills are easy. No more confusion, no more fright, no more being a step behind everybody else in database technology. Here is just some of the information you will learn in this course:

The basics of databases - what they are, how they work, and how they structure data.
Data management - How do we keep millions of pieces of information organized and up-to-date?
Data structure - How do we organize data so that our database is protected from anomalies?
How to structure the three types of relationships between tables - one-to-one, one-to-many, and many-to-many. Each with practical examples.

I didn't create this course to sell you something that's going to waste your time. I created this course because I have a passion for databases and I love teaching in a fun way. This course is fun, easy to follow, and worth every penny.

Who this course is for:

This Database Design course is for beginners who have no prior experience with databases or database design. This course will only go over designing. Avoid this course if you are more experienced or are looking to actually use SQL to program a database.

Database Relationships

What you'll learn

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Course content

Introduction1 lecture • 1min

Introduction to Database Concepts6 lectures • 22min

Let's Conceptualize!5 lectures • 15min

Foreign keys in More Detail3 lectures • 21min

The Relationships!6 lectures • 43min

Conclusion1 lecture • 1min

Requirements

Description

Who this course is for: