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CS380

PHP and MySQL

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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.

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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.

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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.

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PHP MySQL functions

name description

mysql_connect connects to a database server

mysql_select_db chooses which database on server to use (similar to SQL USE database; command)

mysql_query performs a SQL query on the database

mysql_real_escape_string encodes a value to make it safe for use in a query

mysql_fetch_array, ... returns the query's next result row as an associative array

mysql_close closes a connection to a database

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Other MySQL PHP functions

name description

mysql_num_rows returns number of rows matched by the query

mysql_num_fields returns number of columns per result in the query

mysql_list_dbs returns a list of databases on this server

mysql_list_tables returns a list of tables in current database

mysql_list_fields returns a list of fields in the current data

complete list

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Insert in a database

Insert new values to columns of a table

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

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Practice: Bookorama

Query database using forms Insert data in database

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CS380

Appendix A

Database Design

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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.

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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

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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, email, 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

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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

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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

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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

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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?

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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