PHP and MySQL CS380 1

How Web Site Architectures Work  User’s browser sends HTTP request.  The request may be a form where the action is to call PHP code (ex. results.php).  Web server receives the request.  Web server passes the file (results.php) to the PHP engine.  PHP engine parses the script.  PHP opens connection to MySQL server if needed.  PHP sends query to database server. CS380 2

How Web Site Architectures Work  Database server processes the query.  Database sends back results to PHP server.  PHP formats data that it received from database server nicely for HTML.  PHP engine finishes running script.  PHP returns HTML to the web server.  Web server passes HTML back to the browser. CS380 3

Querying a database from the web  Check and filter data coming from the user.  Setup connection to the appropriate database.  Query the database.  Retrieve the results.  Present the results back to user. CS380 4

PHP MySQL functions CS380 5

Other MySQL PHP functions CS380 6

Insert in a database  Insert new values to columns of a table CS380 7 INSERT INTO tbl_name (col1,col2) VALUES(15,col1*2); SQL $isbn=$_POST['isbn']; $author=$_POST['author']; $title=$_POST['title']; $price=$_POST['price']; $query = "insert into books values ('".$isbn."', '".$author."', '".$title."', '".$price."')"; SQL

Practice: Bookorama  Query database using forms  Insert data in database CS380 8

Appendix A Database Design CS380 9

Database design principles  database design: the act of deciding the schema for a database  database schema: a description of what tables a database should have, what columns each table should contain, which columns' values must be unique, etc. CS380 10

Database design principles  some database design principles:  keep it simple, stupid (KISS)  provide an identifier by which any row can be uniquely fetched  eliminate redundancy, especially of lengthy data (strings)  integers are smaller than strings and better to repeat  integers can be compared/searched more quickly than strings, real numbers CS380 11

First database design  what's good and bad about this design?  good: simple (one table), can see all data in one place  bad: redundancy (name, , course repeated frequently)  bad: most searches (e.g. find a student's courses) will have to rely on string comparisons  bad: there is no single column whose value will be unique in each row 12

Second database design  splitting data into multiple tables avoids redundancy  normalizing: splitting tables to improve structure and remove redundancy / anomalies  normalized tables are often linked by unique integer IDs 13

Second database design  primary key: a table column guaranteed to be unique for each record  record in Student table with id of 888 is Lisa Simpson's student info 14 CS380

Second database design  records of one table may be associated with record(s) in another table  foreign key: a column in table A that stores a value of a primary key from another table B  records in Grade table with student_id of 888 are Lisa Simpson's course grades 15

Design question  suppose we want to keep track of the teachers who teach each course  e.g. Ms. Krabappel always teaches CSE 142 and INFO 100  e.g. Ms. Hoover always teaches CSE 143  e.g. Mr. Stepp always teaches CSE 190M  what tables and/or columns should we add to the database? 16

Design answer  add a teachers table containing information about instructors  link this to courses by teacher IDs  why not just skip the teachers table and put the teacher's name as a column in courses?  repeated teacher names are redundant and large in size 17