Relationships

Name: Relationships
Author: Daniel Hanks

Navigate relationships within databases

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Course: On-Demand

This lesson, we're gonna discuss a one-to-one one-to-many and many-to-many. First we're gonna focus on one-to-one relationships. These are probably the easiest to visualize but the least commonly used. So before I explain an example of that I wanna go into our Management Studio software here and there is a little folder here called Database Diagrams. And you can right click on that and go to New Database Diagram. And it may not be installed by default. So just say yes and then you'll have to either exit out of the program and go back in to get it to work or reboot your machine. But once you do, you should get this add table menu here. And here's my three tables that we've created in this database. I'm just gonna add these two, 'cause I don't really wanna use the import table just to show you. We can close that. And you can see the table has a relationship already established here from what we did before. Back to one-to-one relationships. So an example of that could be one patient having a single patient ID. And where that would be useful is where you wanna limit access to data to only users that need access. So if your patient, John Doe, only has access to his own medical record. Then a one-to-one relationship would make it so only John Doe has access to it. So if I wanted to visualize that one-to-one relationship I can use this database diagrams, you can use it to create tables or add a new table, right through here by right clicking in workspace and clicking new table. I can name this patient, just for my example. And this will be an ID, which is an integer since it's an ID and we would allow nulls. I'll just say name. Varcher. That's fine for here. We'll add another table. Medical records. Main ID. Then we would link it with a patient ID. These integers. And I could make this my primary key. Perhaps I don't want that, have to put it here. So that my ID is my primary key. And using this, it's actually a little bit more convenient. You can just drag the key right over to patient ID. And it brings up that tables and columns wizard that we were using before to establish a relationship. And that all looks good, patient with ID, medical records with patient ID. Said okay. And there you go. That's established a relationship there. And that would be an example of a one-to-one since it's an ID going with the patient ID and not anything else in the table. So that should do it for one-to-one relationships. Next, we're gonna look at one-to-many relationships which is actually the most common of the relationships used.

Beginner Provider : Daniel Hanks 3 Lessons · 6m in Arabic, German, English, Spanish, French, Portuguese, Urdu, Chinese

Course Description

This course will review relationships. This includes one-to-one, one-to-many, and many-to-many relationships. You’ll use your database software to look at database diagrams and understand the difference between these different relationships.

You’ll learn how to link existing tables and establish relationships between them. You’ll then add tables within the software so you can visualize and understand how new relationships can be established. The lessons will discuss when a certain relationship should be used and will also cover how tables with data relationships will connect. You’ll build simple one-to-one relationships at first, then build up to a more complex one-to-many relationship. Finally, we’ll discuss and visualize the concept of junction tables and how they are used to connect multiple tables within a many-to-many relationship.

What You'll Learn

Distinguish between one-to-one, one-to-many, and many-to-many relationships
Read and interpret database diagrams using your database software
Link existing tables and establish relationships between them
Add new tables in the software to visualize how new relationships can be established
Build simple one-to-one relationships and progress to more complex one-to-many relationships
Apply junction tables to connect multiple tables within a many-to-many relationship

Key Takeaways

The course covers three types of database relationships: one-to-one, one-to-many, and many-to-many.
Database software is used to view database diagrams and understand the differences between relationship types.
The lessons explain when a certain relationship should be used and how tables with data relationships connect.
Learners start by building simple one-to-one relationships and build up to a more complex one-to-many relationship.
Junction tables are used to connect multiple tables within a many-to-many relationship.

Frequently Asked Questions

What types of relationships does this course cover?

It covers one-to-one, one-to-many, and many-to-many relationships, including how and when each should be used.

What will I do with database software in this course?

You will use your database software to look at database diagrams, link existing tables, establish relationships between them, and add new tables to visualize how new relationships can be established.

What are junction tables and where are they covered?

The course discusses and visualizes junction tables, which are used to connect multiple tables within a many-to-many relationship.

What skills does this course build?

It builds skills in database diagrams, database modeling, entity relationship models, relational databases, the relational model, and relational theory.

How is the course structured?

It is organized into three lessons: One-to-One Relationships, One-to-Many Relationships, and Many-to-Many Relationships, progressing from simpler to more complex relationships.