Working with MySQL A290/A590, Fall /07/2014

The MySQL Server A MySQL server can be given SQL commands, executes them, and returns the results to the connected application – Like Apache, we need to assign a port number on the system to MySQL on which it will listen for requests Starting the server Stopping the server

Command Line Interface Starting the MySQL client Commands for looking around in the database –SHOW DATABASES –USE database –SHOW TABLES –DESCRIBE table

Databases Advantages – concurrency – fast access to the data that is transparent to the db user – uses tables, a general data structure that can implement any data model – unified language for accessing and manipulating the data in the database (SQL) Disadvantages – For certain tasks, can be an overkill as far as complexity and storage requirements are concerned

Database Tables A typical database table definition has: – a name – a list of columns and their data types – a list of constraints primary key to ensure uniqueness (if necessary) foreign keys to facilitate relationships w/ other tables indices to facilitate fast look ups

Database Structure For Quizes iddescriptioncreation_date 1Favorite Things Quiz 10/07/ :22 idtextquiz_id 1What is your favorite color? 1 2What is your favorite book? 1 … idtextpoint_valuequestion_id 1Red11 2Green101 … quiz table question table answer table

Data Relationships One-To-Many: the relationship between the quiz and question tables, or question and answer tables – One quiz can have many questions, but a question can only have one associated quiz – One question can have many possible answers, but an answer can have only one associated question

Keeping Track of Users and Their Quizes id password ndiana.edu … iddescriptioncreation_date 1Favorite Things Quiz 10/07/ :22 AM quiz table user table user_idquiz_idscoredate_taken /07/ :00 AM … user_scores table

Table Relationships Many-To-Many: the relationship defined in the user_scores table – One quiz can be taken by many users – One user can take many quizes

Creating The Database Schema CREATE TABLE quiz ( id INT NOT NULL AUTO_INCREMENT, description VARCHAR(255), create_time DATETIME NOT NULL, PRIMARY KEY(id) ) CREATE TABLE question ( id INT NOT NULL AUTO_INCREMENT, text VARCHAR(255), quiz_id INT NOT NULL, PRIMARY KEY (id), FOREIGN KEY (quiz_id) REFERENCES quiz(id) ON DELETE CASCADE ) CREATE TABLE answer ( id INT NOT NULL AUTO_INCREMENT, text VARCHAR(255) NOT NULL, point_value INT NOT NULL, question_id INT NOT NULL, PRIMARY KEY(id), FOREIGN KEY question_id REFERENCES question(id) ON DELETE CASCADE )

Creating the Database Schema CREATE TABLE user ( id INT NOT NULL AUTO_INCREMENT, VARCHAR(255) NOT NULL, password VARCHAR(255) NOT NULL PRIMARY KEY (id) ) CREATE TABLE user_scores ( user_id INT NOT NULL, quiz_id INT NOT NULL, score INT NOT NULL, date_taken DATETIME NOT NULL, PRIMARY KEY (user_id, quiz_id), FOREIGN KEY (user_id) REFERENCES user(id) ON DELETE CASCADE, FOREIGN KEY (quiz_id) REFERENCES quiz(id) ON DELETE CASCADE )

Filling In the Details Data types: – Numbers: INT, LONGINT, NUMERIC, FLOAT, DOUBLE – Strings: VARCHAR( >), TEXT, BLOB – Other: DATETIME NOT NULL vs NULL: whether to allow empty values or not PRIMARY KEY and FOREIGN KEY CASCADE: Keeping the data clean and robust

Viewing and Manipulating Data in MySQL SELECT – SELECT * FROM quiz; – SELECT a.text, a.point_value FROM answer a – SELECT a.text FROM answer a WHERE a.point_value > 2 INSERT – INSERT INTO quiz VALUES (NULL, 'Test Quiz', NOW()) DELETE – DELETE FROM answer WHERE point_value >= 3 UPDATE – UPDATE quiz SET description = 'Test' WHERE id=1

Viewing Data From Multiple Tables How do we view all questions and their answers for a particular quiz iddescriptioncreation_dat e 1Favorite Things Quiz 10/07/ :22 idtextquiz_id 1What is your favorite color? 1 2What is your favorite book? 1 … idtextpoint_valuequestion_id 1Red11 2Green101 …

Using INNER JOIN SELECT quiz.description, q.text, a.text, a.point_value FROM quiz q INNER JOIN question qn ON q.id =qn.quiz_id INNER JOIN answer a ON qn.id=a.question_id

Interface Between Python and MySQL See examples.