Neck-Deep in CRUD with MySQL & PHP Part 1: MySQL

Andrew Bullen – ISL Brian Smith – RAILS

LAMP stack

• Linux – operating system • Apache – web server • MySQL – database management system • PHP – programming language

(The “P” could also be PERL or Python.)

XAMPP

• X – cross-platform • Apache – web server • MySQL – database management system • PHP – programming language • PERL – also included!

Download from apachefriends.org

MySQL

• “My sequel” (also “My ess cue ell”) • Very widely used • SQL = Structured Query Language • SQL has commands and syntax to define and

manipulate data

CRUD

• Create – add new data • Read – retrieve existing data • Update – change existing data • Delete – get rid of existing data

Database

• Database has tables • Table has:

– Columns = fields – Rows = records

• Database has relationships between tables – One-to-one – One-to-many – Many-to-many

Relationships

Hey, let’s build a database!

Create pet_library database

Create genres table

Define columns for genres table

Create pets table

Define columns for pets table

Note: petGenre column needs to be INDEXED.

Add pets -> genres relationship

Set petGenre as a foreign key

Create: Time to add data!

Note: Values of string fields need to be enclosed in single quotes. Do not enclose values of numeric fields in quotes.

Yay!

Let’s add some pets!

Read: Queries to list all pets

SELECT * FROM pets SELECT * FROM pets ORDER BY petName SELECT petName, petDescription FROM pets

Queries to list some pets

SELECT * FROM pets WHERE petName = ‘Spot’ SELECT * FROM pets WHERE petName LIKE ‘S%’ SELECT * FROM pets WHERE petID <> 2

Query with JOIN to include genre

SELECT p.petName, g.genre, p.petDescription FROM pets AS p JOIN genres AS g ON p.petGenre = g.genreID ;

Query for pets and petless genres

SELECT p.petName, g.genre, p.petDescription FROM pets AS p RIGHT JOIN genres AS g ON p.petGenre = g.genreID ;

Update: Wuffles is very old

R.I.P. Wuffles

Try some more UPDATEs

Some suggestions … • Dr. Moreau has changed one of the cats into a

ferret. • Change the name of a pet. • Bring Wuffles back to life! • Budgie? We say “parakeet” here in the USA!

Delete: Weed dogs from the collection

Everyone have at least one dog? Try this: DELETE FROM genres WHERE genreID = 2 (You should get an error.) Now do: DELETE FROM pets WHERE petGenre = 2 And then try again: DELETE FROM genres WHERE genreID = 2

Be careful with DELETE

• If you don’t include a good WHERE condition, you may delete rows that you needed to keep.

Some other dangerous MySQL commands: • TRUNCATE TABLE – deletes all data from table,

but keeps table structure • DROP TABLE – totally deletes table • DROP DATABASE – Guess what that does?

Make regular backups!

Database user accounts

• XAMPP’s default is no password for root user • In the real world:

– Set a strong password for root. Instructions at http://www.scriptarticle.com/2012/07/04/how-to-change-or-reset-xampp-mysql-root-password/

– Add a new user with access only for your database, and connect your website code to the database as that user.

Adding user for pet_library

Allow only necessary permissions

Help and tutorials:

• http://dev.mysql.com/doc/ • http://stackoverflow.com/ • www.w3schools.com/sql/