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PHP with MySQL Essential Training
Illustration by Don Barnett

Relational database tables


From:

PHP with MySQL Essential Training

with Kevin Skoglund

Video: Relational database tables

In this movie we'll learn how relational databases work. The idea behind relational databases is simple but the results are very powerful. Let's imagine for a moment that a subject like about Widget Corp, that we created in the last movie. Let's imagine that it has a set of pages that should be listed under that subject. This is what would be called a one to many relationship. And when describing that relationship, you can say that a subject has many pages and that each page belongs to the subject. In order to understand why having a relationship is important, let's imagine for a moment that when each one of these pages displays on the final public site.
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  1. 4m 8s
    1. Welcome
      1m 0s
    2. Using the exercise files
      3m 8s
  2. 15m 6s
    1. What is PHP?
      3m 52s
    2. The history of PHP
      2m 51s
    3. Why choose PHP?
      4m 10s
    4. Installation overview
      4m 13s
  3. 54m 53s
    1. Overview
      2m 33s
    2. Working with Apache Web Server
      6m 56s
    3. Changing the document root
      7m 24s
    4. Enabling PHP
      6m 16s
    5. Upgrading PHP
      3m 30s
    6. Configuring PHP
      10m 3s
    7. Installing MySQL
      5m 46s
    8. Configuring MySQL
      7m 24s
    9. Text editor
      5m 1s
  4. 31m 25s
    1. Overview
      3m 27s
    2. Installing WampServer
      5m 46s
    3. Finding the document root
      2m 24s
    4. Configuring PHP
      8m 12s
    5. Configuring MySQL
      5m 45s
    6. Text editor
      5m 51s
  5. 19m 12s
    1. Embedding PHP code on a page
      6m 43s
    2. Outputting dynamic text
      5m 55s
    3. The operational trail
      2m 27s
    4. Inserting code comments
      4m 7s
  6. 1h 18m
    1. Variables
      7m 50s
    2. Strings
      4m 38s
    3. String functions
      8m 54s
    4. Numbers part one: Integers
      6m 27s
    5. Numbers part two: Floating points
      5m 25s
    6. Arrays
      10m 0s
    7. Associative arrays
      6m 37s
    8. Array functions
      6m 33s
    9. Booleans
      3m 50s
    10. NULL and empty
      5m 15s
    11. Type juggling and casting
      8m 27s
    12. Constants
      4m 43s
  7. 27m 37s
    1. If statements
      6m 0s
    2. Else and elseif statements
      4m 16s
    3. Logical operators
      7m 30s
    4. Switch statements
      9m 51s
  8. 42m 15s
    1. While loops
      8m 41s
    2. For loops
      5m 59s
    3. Foreach loops
      8m 16s
    4. Continue
      8m 28s
    5. Break
      4m 8s
    6. Understanding array pointers
      6m 43s
  9. 37m 25s
    1. Defining functions
      8m 25s
    2. Function arguments
      5m 32s
    3. Returning values from a function
      7m 33s
    4. Multiple return values
      4m 53s
    5. Scope and global variables
      6m 2s
    6. Setting default argument values
      5m 0s
  10. 20m 18s
    1. Common problems
      3m 47s
    2. Warnings and errors
      8m 36s
    3. Debugging and troubleshooting
      7m 55s
  11. 57m 57s
    1. Links and URLs
      5m 33s
    2. Using GET values
      5m 35s
    3. Encoding GET values
      8m 41s
    4. Encoding for HTML
      9m 26s
    5. Including and requiring files
      7m 40s
    6. Modifying headers
      6m 45s
    7. Page redirection
      6m 43s
    8. Output buffering
      7m 34s
  12. 1h 3m
    1. Building forms
      7m 28s
    2. Detecting form submissions
      5m 59s
    3. Single-page form processing
      7m 57s
    4. Validating form values
      10m 40s
    5. Problems with validation logic
      9m 54s
    6. Displaying validation errors
      7m 23s
    7. Custom validation functions
      6m 28s
    8. Single-page form with validations
      7m 25s
  13. 28m 5s
    1. Working with cookies
      2m 49s
    2. Setting cookie values
      5m 55s
    3. Reading cookie values
      6m 1s
    4. Unsetting cookie values
      4m 51s
    5. Working with sessions
      8m 29s
  14. 48m 39s
    1. MySQL introduction
      6m 43s
    2. Creating a database
      7m 41s
    3. Creating a database table
      7m 42s
    4. CRUD in MySQL
      5m 48s
    5. Populating a MySQL database
      7m 32s
    6. Relational database tables
      6m 40s
    7. Populating the relational table
      6m 33s
  15. 56m 4s
    1. Database APIs in PHP
      4m 51s
    2. Connecting to MySQL with PHP
      7m 45s
    3. Retrieving data from MySQL
      8m 47s
    4. Working with retrieved data
      6m 12s
    5. Creating records with PHP
      6m 58s
    6. Updating and deleting records with PHP
      9m 6s
    7. SQL injection
      3m 5s
    8. Escaping strings for MySQL
      6m 45s
    9. Introducing prepared statements
      2m 35s
  16. 35m 58s
    1. Blueprinting the application
      7m 19s
    2. Building the CMS database
      5m 14s
    3. Establishing your work area
      4m 38s
    4. Creating and styling the first page
      4m 22s
    5. Making page assets reusable
      6m 36s
    6. Connecting the application to the database
      7m 49s
  17. 32m 49s
    1. Adding pages to the navigation subjects
      5m 58s
    2. Refactoring the navigation
      6m 7s
    3. Selecting pages from the navigation
      6m 2s
    4. Highlighting the current page
      5m 26s
    5. Moving the navigation to a function
      9m 16s
  18. 1h 45m
    1. Finding a subject in the database
      9m 48s
    2. Refactoring the page selection
      10m 52s
    3. Creating a new subject form
      6m 55s
    4. Processing form values and adding subjects
      11m 20s
    5. Passing data in the session
      9m 16s
    6. Validating form values
      9m 40s
    7. Creating an edit subject form
      8m 30s
    8. Using single-page submission
      7m 44s
    9. Deleting a subject
      9m 44s
    10. Cleaning up
      10m 37s
    11. Assignment: Pages CRUD
      4m 30s
    12. Assignment results: Pages CRUD
      6m 10s
  19. 39m 26s
    1. The public appearance
      8m 52s
    2. Using a context for conditional code
      11m 37s
    3. Adding a default subject behavior
      6m 9s
    4. The public content area
      5m 51s
    5. Protecting page visibility
      6m 57s
  20. 1h 3m
    1. User authentication overview
      4m 3s
    2. Admin CRUD
      8m 41s
    3. Encrypting passwords
      7m 26s
    4. Salting passwords
      5m 42s
    5. Adding password encryption to CMS
      11m 54s
    6. New PHP password functions
      3m 13s
    7. Creating a login system
      11m 28s
    8. Checking for authorization
      5m 48s
    9. Creating a logout page
      5m 40s
  21. 2m 4s
    1. Next steps
      2m 4s

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PHP with MySQL Essential Training
14h 24m Beginner Jun 04, 2013

Viewers: in countries Watching now:

PHP is a popular, reliable programming language at the foundation of many smart, data-driven websites. This comprehensive course from Kevin Skoglund helps developers learn the basics of PHP (including variables, logical expressions, loops, and functions), understand how to connect PHP to a MySQL database, and gain experience developing a complete web application with site navigation, form validation, and a password-protected admin area. Kevin also covers the basic CRUD routines for updating a database, debugging techniques, and usable user interfaces. Along the way, he provides practical advice, offers examples of best practices, and demonstrates refactoring techniques to improve existing code.

Topics include:
  • What is PHP?
  • Installing and configuring PHP and MySQL
  • Exploring data types
  • Controlling code with logical expressions and loops
  • Using PHP's built-in functions
  • Writing custom functions
  • Building dynamic webpages
  • Working with forms and form data
  • Using cookies and sessions to store data
  • Connecting to MySQL with PHP
  • Creating and editing database records
  • Building a content management system
  • Adding user authentication
Subjects:
Developer Servers Programming Languages Web Development
Software:
MySQL PHP
Author:
Kevin Skoglund

Relational database tables

In this movie we'll learn how relational databases work. The idea behind relational databases is simple but the results are very powerful. Let's imagine for a moment that a subject like about Widget Corp, that we created in the last movie. Let's imagine that it has a set of pages that should be listed under that subject. This is what would be called a one to many relationship. And when describing that relationship, you can say that a subject has many pages and that each page belongs to the subject. In order to understand why having a relationship is important, let's imagine for a moment that when each one of these pages displays on the final public site.

Then it also needs to display the subject name along with the page, the subject that it belongs to. So we could create a table for our pages and we could give that table a column called subject name. And then we could store the subject name with each and every page. But then what happens if the subject name changes at some point, we want to make a change to it? We'd have to change the name field in the subjects table and also change the subject name field for every single page in the pages table that has to do with that subject. It's much better and much more efficient if the page can just refer to the subject's table and get the data from its name field whenever it needs it.

Then if we want to make a change, we're just changing the data in one place: in the subject's table. And as we've seen with functions and loops and including files, not repeating yourself is almost always a good idea. It's better to write it once and then access it whenever it's needed. The same thing is true here. So now that we understand why we need these relationships. How do we actually go about creating relationships in MySQL? We're going to use a foreign key and you'll remember that before I gave you a definition of a foreign key was a table column whos values reference rose in another table.

So let's see how that works. Let's say we have our subjects table. We've seen that before. We have About Widget Corp. And then we have another table that we haven't created yet called pages. And it also has an ID, a menu name, position, and visible. Plus it has another column for content, which is the actual content that we're going to display to the user. That's the real meat of our content management system. Now, right now, these two tables don't have any relationship whatsoever. What I need to do is add a column to one of them where the values will reference rows in the other table.

And we're going to do that on a one to many relationship. We're going to do that on the many side, not on the one side but on the many side, we'll add a column. So I'm going to add a column between id and menu name called subject_id and it has a value of one that relates to a value of one that we have over in the subjects table. So now we have a relationship and that's because now if I have a page and I want to know what subject it belongs to. Let's say I want to find its menu name. Well then I can just ask my SQL to make a new query.

And query for the subject where ID equals one. How do I know that ID? Well it's stored in my subject ID field. It's right there. That's the one that I use. I ask you to make a new query, I get back the subject, I find its menu name, and I can display it on the page. And it works in reverse too. If I have a subject and I want to know all of the pages that belong to that subject. Let's say I want to generate a list of them, well, then I can ask my SQL generate a query and return to me all pages where the subject ID is the same ID as what I have in this case one. And I'll get back a list of all of those pages.

These now are relational database tables. Let's go back into my SQL and let's create this new pages table and relate it to our subjects table. Okay. So I'm in my SQL already and I've created my subjects table and populated it. Now, I'm going to create my pages table. So, I'm just going to clear my screen and we're going to do a new create tables statement. Create table pages and then in parenthesis I'm going to put those pairs of the name at the column followed by the definition. So just like before, we're going to us an ID of INT size 11, not null and auto_increment comma and make sure you spelled all that right especially increment.

Make sure you spell that correctly, hit Return and then the next one is going to be my foreign key. So that's subject_id, that's how I'm going to know it's related to subjects because subject, singular, id relates to subjects plural, the table. And it's going to be integer of 11, also not null and then menu name. That's going to also be a varchar of type 30, just like we did for the other one, not null. Position int 3, not null. And visible, it's going to be a tiny int 1, that will be my Boulian. And then for the next one, this is one that we didn't have before. This is going to be content.

That's the content of the page and that can be quite large. So varchar probably isn't what we want cause varchar typically is limited to 255 characters. It doesn't have to be. It can go much larger than that. But once you start getting over that size, you really should start thinking about having something else and text is what we want. That's the name of field, is text and that's an unlimited amount of text or at least close enough to unlimited that you don't need to worry about it. going to be a lot of text can go in that field. And then I'll hit Return. We're still going to have primary key defined just like we did before, id. But this time instead of just ending it, we're going to put a comma and I'm going to add one more here, which is index on subject ID. Now this is a foreign key already without me specifying. Were going to use it as a foreign key to this other table. Index is going to tell MySQL that it should also create an index for it, for fast look ups.

It automatically builds an index for us for the primary key. It always does that because it wants to be able to look up things quickly and the primary key's the main way that it does that. So it gives us that index for free but any other index we want to use we're going to need to add ourselves. So index on subject ID is going to tell it hey this is something you're going to be using often so go ahead and create an index for it. And you're always going to want to create indexes for your foreign keys. Okay and let's hit Return. We'll close our parenthesis and put a semicolon.

And now we'll create our pages table to show tables. So we can see it. And there we go. We see our pages table. And we can say show columns from pages. Now we can see what it looks like. And you'll see now that in addition to having our subject column here, it also tells us that we have a index on that. So now we have two tables in our database and we have a relationship between them. But we don't have any data that's actually related yet. The next movie, we'll see how to add that.

Find answers to the most frequently asked questions about PHP with MySQL Essential Training.


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Q: This course was revised on 6/4/2013. What changed?
A: The old version of this course was 6 years old and it was time for a complete revision, using PHP 5.4. (The tutorials will work with any version of PHP and covers any differences you might encounter). The author has also added updated installation instructions for Mac OS X Mountain Lion and Windows 8. The topics and end project are the same, but the code is slightly different. It also addresses frequently asked questions from the previous version.
 
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