Creating databases for web applications

Regular expression homeworkDatabase datatypes. Creating database

Homework: Create tables in database. Add records to database.

Homework• Design (and test) regular expressions to search

for each of the following:– a string with "curley", "larry", or "moe" somewhere in

it. Case does not matter.– a dollar amount: for example, accept $2.59, 10, 1,200

and reject 1.2345, 3.4.5.– Valid date in MM/DD/YYYY or MM/DD/YY format (for

example, 14/2/2001 would not be acceptable. See if you can allow 1/4/04 as well as 01/04/2004.

– For state caps quiz: New York or NY, St. Paul or Saint Paul

– accept Obama, Barack Obama, Barack Hussein Obama, but NOT Michelle Obama, Malia Obama, etc.

Homework, cont.

• Design (create) 3 questions for a quiz show game and design regular expressions that validate the answers. The challenge is to be no more and no less exacting than a human checker.

Database design• Not easy!• Will discuss formal methods next week• Review: databases are made up of

– Tables: tables made up of • Records: records made up of fields

• Speaking of rows and columns is misleading• Critical issue: fixed number of fields, though a

specific field may be optional (aka not required)– NOT NULL in MySQL jargon means required!– MySQL does support variable length strings.

Data types

• Terminology varies for different DBMS products

• Performance (speed) of operations varies with different datatypes

• Size varies with different datatypes• Performance and size limits are points of

competition among the different products

MySQL datatypes: numbers

• INT (aka INTEGER), can be UNSIGNED (Size 4 bytes = 32 bits)

• TINYINT, SMALLINT, MEDIUMINT, BIGINT– Different sizes

• float (4 bytes), double (8 bytes), can specify precision within these limits

• more

MySQL datatypes, strings

• CHAR(specified length)• VARCHAR(maximum length)• TINYBLOB short, variable length string,

up to 255 characters• BLOB, TEXT variable length string• MEDIUMBLOB, MEDIUMTEXT,

LONGBLOB, LONGTEXT

MySQL datatypes: enum

• ENUM– Specify one of a set of values– Stored as an integer, with 0 indicated unset or

not in the specified set– Doing this may be more efficient because

built-in MySQL routines do the searching

MySQL datatypes: date/time

• DATE• TIME• DATETIME• YEAR• TIMESTAMP

Tables• Specify one field as the primary key• Primary keys are unique IN THAT TABLE

– Let the DBMS create the primary key OR– Depend on intrinsic value that is guaranteed to be

unique• Email addresses• ISBN numbers• ?

• A field in one table may be a foreign key. This is a reference to a primary key in another table (or this table). MORE ON THIS LATER.

Database

• Assume database itself is created for us AND we have permissions to create new tables.

• NOTE: permissions can be set by MySQL commands, including queries sent by php.

• Start off talking general SQL and then specific php and MySQL

Create table example

• CREATE TABLE movies (mid INT NOT NULL AUTO_INCREMENT PRIMARY KEY,mname CHAR(30),

mdesc TEXT,myear YEAR

)

Create table example

CREATE TABLE players ( pid INT NOT NULL AUTO_INCREMENT PRIMARY KEY,pname CHAR(30),

score INT NOT NULL,lastplayed DATE

)

Create example

CREATE TABLE games (gid INT NOT NULL AUTO_INCREMENT PRIMARY KEY,pid INT,gtime TIMESTAMP,score INT

) The pid field will refer to / have the value of

the pid field (the primary key) of a specific player. Here in this table, it is called a foreign key.

Foreign keys• Some versions of MySQL (and other DBMS)

have ways to specify the the pid value is a foreign key

pid INT REFERENCE players

• The DBMS will check to make sure it is a valid value.

• Since the php coding should guarantee this, I omit this from my examples.– Extra credit opportunity for posting on this.

Class Exercises

Write the CREATE TABLE statement for a table• MySQL generated id, course 'number'

(MAT3530.45), name, cap, credits, teacher, time slot, building– Why can't MAT3530.45 be the primary key?

• Published book: the ISBN number can serve as primary key, title, year of publication

• Your own idea

Now, show the code• Application includes 5 files!

– createatable.php• Drops table and creates new one. No problem if table does

not exist.– entertable.html

• Points to inputmovies.php in form action– inputmovies.php

• Inserts record using the passed form data– connectcode.php

• File for connecting to database: examples used different names, such as opendb.php

– showmovies.php• Retrieves records from table and displays them

connectcode.php<?php$link = mysql_connect('localhost',

'WKILLORAN', 'PASSWORD'); if (!$link) { die('Not connected : ' . mysql_error()); } $DBif (!mysql_select_db('WKILLORAN_DB', $link)) { echo 'Could not select database'; exit; }?>

Comment• Put the connect code in a file by itself, to

be included– require (connectcode.php);

• This means that you can share the other files and

• Just need to change one file.

• NOTE: check my use of $Dbname and $link.

<?phpfunction createtable($tname,$fields) {global $DBname, $link;$query = "DROP TABLE $tname";mysql_query($query);$query="CREATE TABLE ".$tname."(".$fields.")";if (mysql_query($query)) { print ("The table, $tname, was created

successfully.<br>\n"); }else { print ("The table, $tname, was not created. <br>\n"); }}?>

<html><head><title>Creating movie table </title> </head> <body>

<?phprequire("connectcode.php");$tname = "movies";$fields = "mid INT NOT NULL

AUTO_INCREMENT PRIMARY KEY, mname CHAR(30), mdesc TEXT, myear YEAR";

createtable($tname, $fields);mysql_close($link);?></body> </html>

Add records to table• INSERT INTO movies VALUES (

0, 'WALL-E','computer generated animation, with environmental theme',2008)

OR• INSERT INTO movies SET

mname = 'WALL-E', mdesc = ' 'computer generated animation, with environmental theme', myear = 2009 MySQL will generate the

mid

HTML form<html><head><title>Input movies

</title></head> <body><form action="inputmovies.php">Movie Name <input type="text"

name="mn"/>Description <textarea name="desc"

rows="10" cols="50">…</textarea><input type="input" name="my" /><input type="submit" value="STORE"/></form> </body> </html>

php handler to do INSERT

<?phprequire("connectcode.php");$mn =$_GET['mn'];$desc=$_GET['desc'];$my = $_GET['my'];$query="INSERT INTO movies VALUES (";$query.="'0','$mn','$desc',$my)";

Value of variables $mn, $desc,$my are made part of string

Comments• The connectcode.php has database name and

password. It sets $link used later.• NOTE: trick of php that variable names inside

double quotes get evaluated.• NOTE: the presence of the single quotes around

strings. These are required by MySQL (and other DBMS)

• Code needs to be improved: What if name or description had quotes or slashes? Try it and then add

$desc =addslashes($desc);

if (mysql_query($query)) {print ("movie added successfully");

} Else { print ("failure to add movie "); }mysql_close(….); //this depends on db link?>

showmovies.php<html> <head><title>Show player scores</title>

</head><body><?phprequire("connectcode.php");$query="SELECT * FROM movies";$rs=mysql_query( $query);while ($row=mysql_fetch_array($rs)){ print($row['mname'] . " (" .$row['myear'] . "): <br/> "); print($row['mdesc']); print("<hr/>"); }?></body> </html>

Standard way to put db connect code in one place

Comments

• [Go over this again next class]• Put the db connection code in separate

file, to be included in all other files• The fields are extracted by name.

– Chose not to extract and display mid• The $rs produced by the SELECT query is

called a recordset. It is like a table. Its rows can be extracted one at a time.

More SQL

• ALTER: this is for changing or adding a field definition

• DROP: this is dropping a table. This is good to do before creating a table, just in case you already did it OR don't drop it, and check for errors.

Caution

• My songs with features database contains nonsense that I put in to quickly test the applications.

• Also, no provision for duplicates or near duplicates…

Songs with features examples• http://newmedia.purchase.edu/~Jeanine/db/example/

addsong.html– action=addsong.php

• http://newmedia.purchase.edu/~Jeanine/db/example/addfeature.html– action=addfeature.php

• http://newmedia.purchase.edu/~Jeanine/db/example/addfeaturestosong1.php– action=addfeaturestosong2.php

• http://newmedia.purchase.edu/~Jeanine/db/example/findothers1.php– action=findothers2.php

• Note: last two need to go to database to present a form for user.

Remove application

• Need to remove song PLUS all the feature/song records

• http://newmedia.purchase.edu/~Jeanine/db/example/removesong1.php

from removesong1.phpSelect a song to be deleted with its features<hr/> <form action="removesong2.php"><table><?phprequire("opendbe.php");$query="Select * from songs";$result=mysql_db_query($DBname, $query, $link);while ($row=mysql_fetch_array($result)) { print("<tr>"); print("<td> <input type='radio' name='song' value='".

$row['sid']."'/>"); print ($row['sname'] ."</td><td>".$row['sdesc']."</td><td>".

$row['syear']."</td></tr>"); }?></table> <input type="submit" value="PICK SONG TO BE

DELETED"/> </form>

from removesong2.php<?phprequire("opendbe.php");$sid=$_GET["song"];$query = "Delete from songs where sid='$sid' limit 1";print ($query);$result = mysql_db_query($DBname,$query,$link);if ($result) {

print("The song $sid was deleted.<br>\n"); } else {

print ("The song $sid was not deleted. <br>\n"); }$query = "Delete from featuresinsongs where sid='$sid'";$result = mysql_db_query($DBname,$query,$link);if ($result) {print("The features for song $sid were deleted.<br>\n"); } else { print ("The features for song $sid were NOT successfully

added. <br>\n"); }?>

Notes

• The bad results let me know that I had the name of the tables wrong!– song for songs– featuresinsong for featuresinsongs

Who are the agents?

• In existing find similar songs applications, the assigning of features may not be an end user function…..

Homework• Confirm that you can access or create a database• Write php scripts to create table• Write html and php to INSERT records• Write php to display whole table• Use songs, movies model and posted on-line sources!

– Post comments– Improve appearance– Extra credit: insert default values. Do validation.

• Look up syntax and write php with ALTER and DROP queries.

• USE SOURCES!!!