TweetFollow Us on Twitter

Programming and MySQL

Volume Number: 20 (2004)
Issue Number: 3
Column Tag: Programming

Untangling the Web

by Kevin Hemenway, Imitating Conspirator

Programming and MySQL

Modifying our MySQL database with the shell and PHP.

We finally added information into our MySQL database last issue, but in a rather infantile way: by writing all the SQL statements (like those seen in Listing 1) into a text file and then passing them to MySQL with a command line, mysql mactech < mactech-insert.sql, which completes silently when successful. This is certainly helpful if we're passing default information to be initialized in newly created databases, but not very useful if we want to programmatically access the information within.

Listing 1: Three new SQL INSERT statements for our database.

mactech-insert.sql
INSERT INTO books
   SET publication = "2000-00-00",
       title = "Object Oriented Perl";
       
INSERT INTO books
   SET publication = "1999-00-00",
       title = "MyEssQueEll";
       
INSERT INTO books
   SET publication = "2003-00-00",
       title = "PHP and MySQL Web Development";

In this article, we'll talk about two more ways to manipulate data: through the MySQL interactive shell, and via PHP's built in database functions. First up, let's walkthrough the interactive shell, which is quite helpful for quickly testing out new SQL statements or applying immediate fixes without new code overhead and development.

The MySQL Interactive Shell

Starting up the MySQL interactive shell is mindlessly simple. Just type mysql and you'll be shown a mysql> prompt, similar to the shell prompt you see when you first enter the Terminal. Since we've yet to specify a database, we're in a sort of limbo: MySQL knows we're here, but we've yet to tell it anything of import. First we'll show which databases have been configured, choose which one we'd like to work with, and then ask for a table listing:

:~ > mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2 to server version: 4.0.15

Type 'help;' or '\h' for help.
Type '\c' to clear the buffer.

mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| mactech            |
| mysql              |
| test               |
+--------------------+
3 rows in set (0.26 sec)

mysql> USE mactech;
Reading table information for completion of
table and column names. You can turn off this
feature to get a quicker startup with -A.

Database changed
mysql> SHOW TABLES;
+------------------------------------------+
| Tables_in_mactech                        |
+------------------------------------------+
| books                                    |
| person                                   |
| relationships                            |
+------------------------------------------+
3 rows in set (0.05 sec)

The most obvious fact from the above is that all SQL commands must end with a semi-colon. If you happen to forget that termination, MySQL will change its shell prompt to show you it's waiting patiently for a complete command. The following is the same command as before, only split with new lines. Notice the prompt indicating an incomplete statement:

mysql> SHOW
    -> TABLES
    -> ;

A good portion of readers will know that the shell opened by the Terminal gives you command line history (press the UP arrow to see commands you've previously typed) as well as file or directory completion (press TAB after typing the first few letters). MySQL also supports these time-savers: pressing UP will show you SQLs you've typed previously, and pressing TAB when typing a table or column name will auto-complete the nearest match.

In our previous work with SQL, we've touched on the INSERT, UPDATE, and DELETE commands. We've yet to touch on the most often used, however, which is SELECT. While our previous statements have focused on adding, modifying, or deleting data, the sole purpose of SELECT is for displaying:

mysql> SELECT * FROM books;
+----+-------------------------------+-------------+
| id | title                         | publication |
+----+-------------------------------+-------------+
|  1 | Spidering Hacks               | 2003-11-01  |
|  2 | Mac OS X Hacks                | 2003-04-01  |
|  3 | Object Oriented Perl          | 2000-00-00  |
|  4 | MyEssQueEll                   | 1999-00-00  |
|  5 | PHP and MySQL Web Development | 2003-00-00  |
+----+-------------------------------+-------------+
5 rows in set (0.00 sec)

mysql> SELECT title, name FROM person;
+-------+----------------+
| title | name           |
+-------+----------------+
| Mr.   | Kevin Hemenway |
+-------+----------------+
1 row in set (0.00 sec)

mysql> SELECT * FROM relationships WHERE book_id = '2';
+-----------+----------+
| person_id | book_id  |
+-----------+----------+
|         1 |       2  |
+-----------+----------+
1 row in set (0.05 sec)

The above shows three different variants of a SELECT statement--many more are possible. The first is the easiest to understand: "select everything from the books table". The second is an example of specifying only the columns you want to see, in any order. Even though title came after name in our original CREATE statement (last issue), SELECT allows us to reorder things however we decide best. The third statement is an example of more intimately specifying which exact rows you'd like to retrieve.

Comparing the above walkthrough to the command line we entered last issue (mysql mactech < mactech-insert.sql) gives us a better understanding of what's going on. We specify the database to connect to (mactech; similar to USE mactech in the MySQL shell), and then send a bunch of SQL commands in a batch, as opposed to manually entering them one at a time. It doesn't take a giant leap of faith to realize that we can save the USE database step by specifying it on the command line:

~ > mysql mactech
Reading table information for completion of
table and column names. You can turn off this
feature to get a quicker startup with -A.

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2 to server version: 4.0.15

Type 'help;' or '\h' for help.
Type '\c' to clear the buffer.

mysql> UPdAtE books SET title = "MySQL"
    -> where title = "MyEssQueEll";
Query OK, 1 row affected (0.02 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SeLeCT id, title FRoM
    -> books WHERE title LIKE '%SQL%';
+----+-------------------------------+
| id | title                         |
+----+-------------------------------+
| 4  | MySQL                         |
| 5  | PHP and MySQL Web Development |
+----+-------------------------------+
2 rows in set (0.30 sec)

The previous listing shows an example of entering the MySQL interactive shell with a database already selected, updating a row of misspelling in our previous INSERT (Listing 1), and then getting a pattern match with LIKE. The % characters are boundary placeholders for "anything or nothing", so our final statement finds the letters "SQL" in the beginning, middle, or end of a title. Changing "SQL" to "my" would return the same set of results, confirming that LIKE searches are case-insensitive.

Up until now, all our SQL commands have used capital letters, but you'll notice that they too are case-insensitive. For clarity, I prefer uppercase SQL: it just makes things easier to mentally and visually parse after long hours of fevered coding.

Accessing MySQL From PHP

Our next step is to access our mactech database programmatically with PHP. You'll notice some similarities with the above interactive shell process: we connect to MySQL, choose a database, and issue some SQL queries. You'll note that we're passing the MySQL username and password we created with mysql_setpermission a few columns back. This is important for security: just like you don't want your sister messing with your personal files, you don't want to make it too easy for web interlopers to affect the various databases you maintain. In most cases, once you're finished developing an application, you'd tighten the user's permission even further (say, to restrict DELETE and DROP access).

Save the contents of Listing 2 into /Library/WebServer/Documents:

Listing 2: PHP code for accessing our MySQL database.

db_access.php
<h1>MySQL Database Access in PHP</h1>
<?php
   $dbh = mysql_connect("localhost","favemarksman","***")
     or die ("There was an error connecting to MySQL.");
?>

Before we delve deeper into our code, I wanted to show you a one-character-difference that can be used to improve security. Astute readers will notice that even though I meant davemarksman (the MySQL user created a few issues ago) I mistyped as favemarksman:


Figure 1: An error occurred during the database connection.

Here's the problem: if someone comes to our site and triggers this error message, we've freely given them four pieces of valuable information that can be used against us for exploitive purposes. We've told them we're using MySQL as a database, that it's installed on the same machine as the web server, that there's (possibly) a user named favemarksman (a similar error would occur if the username was correct, but not the password), and revealed a directory path (which, in this case, infers we're using OS X, a fifth fact).

Listing 3 contains a much stronger version of our code, which removes any mention of the technology being used, and stops MySQL from spitting useful information to our visitors. The real magic happens with the @ symbol before our function name: using it will silence any automatically visible errors. This makes for more secure code, as well as a more professional web site (i.e., what impression does it leave visitors if they see nothing but errors?)

Listing 3: Revised PHP code for accessing our MySQL database.

db_access.php, revised
<h1>Database Access in PHP</h1>

<?php
   $dbh = @mysql_connect("localhost","favemarksman","***")
     or die ("An error has occurred. Please report this.");
?>

The revised output is shown in Figure 2:


Figure 2: No more information disclosure. Much better.

With that out of the way, we can now accomplish something. Listing 4 contains complete (but simple) PHP code to insert some information into the mactech database, view it, and then DELETE a bit. As with most programming, there are many ways this can be done: more information about the different mysql_ functions we've not shown can be found at the PHP web site: http://www.php.net/manual/en/ref.mysql.php.

Listing 4: Finished PHP code for accessing our MySQL database.

db_access.php, finished
<h1>Database Access in PHP</h1>

<?php

   // connect to the database server.
   $dbh = @mysql_connect("localhost","davemarksman","***")
     or die ("ERROR: Could not connect to the database!");

   // choose our database.
   @mysql_select_db( "mactech" )
      or die ("ERROR: Could not select our database!");

   // create a SQL statement. Notice that through
   // PHP, the SQL terminating semi-colon is optional.
   $statement = "INSERT INTO person SET
                  name          = 'Dave Mark',
                  date_of_birth = '1901-03-31',
                  title         = 'Intern', 
                  designation   = 'Bullseye Hole Filler'";

   // standard way of executing SQL through PHP.
   $response = @mysql_query( $statement, $dbh );
   
   // mysql_error() would give too much information for
   // a production site, but this is just an example. 
   if (!$response) { print mysql_error () . "\n"; }

   // create and execute another SQL statement.
   $sg_made_out_of = "SELECT * FROM person;";
   $response = @mysql_query( $sg_made_out_of, $dbh );

   // this is one of a few ways to iterate through rows.
   print "<h3>People, List #1</h3>";
   while ( $person = @mysql_fetch_array( $response ) ) {

       // column name is array key.
       print "$person[id], $person[title], 
              $person[name], $person[designation]<br />"; 
   }

   // one more SQL statement, this time a delete.
   $freedom = "DELETE FROM person WHERE name LIKE '%Mar%'";
   $response = @mysql_query( $freedom, $dbh );
 
   // and make sure he's really gone.
   $sg_made_out_of = "SELECT * FROM person;";
   $response = @mysql_query( $sg_made_out_of, $dbh );

   // another way of iterating through rows, only
   // as variables, not hash keys. Could get messy.
   print "<h3>People, List #2</h3>";
   while ( $person = @mysql_fetch_array( $response ) ) {
       extract ( $person ); // make columns variables.
       print "$id, $title $name, $designation<br />"; 
   }

?>

The results of running this script are in Figure 3. Since we're inserting a new record, then deleting it, successive loads will assign the new record an ever-increasing sequential ID, even though the data we're entering is exactly the same.


Figure 3: The final results of our database access in PHP.

Homework Malignments

As is typical in a four-page article, we've barely touched the surface of what PHP can do in regards to database access and handling. Next month, we'll change gears and see how Perl handles the same logic. Until then, contact the teacher at morbus@disobey.com.


Kevin Hemenway, coauthor of Mac OS X Hacks and Spidering Hacks, is better known as Morbus Iff, the creator of disobey.com, which bills itself as "content for the discontented." Publisher and developer of more home cooking than you could ever imagine (like the popular open-sourced aggregator AmphetaDesk, the best-kept gaming secret Gamegrene.com, the ever ignorable Nonsense Network, etc.), he'd rather be nursing his wounds with a swift kick to the head. Contact him at morbus@disobey.com.

 
AAPL
$116.18
Apple Inc.
-0.13
MSFT
$47.62
Microsoft Corpora
-1.08
GOOG
$538.07
Google Inc.
+3.24

MacTech Search:
Community Search:

Software Updates via MacUpdate

StatsBar 1.9 - Monitor system processes...
StatsBar gives you a comprehensive and detailed analysis of the following areas of your Mac: CPU usage Memory usage Disk usage Network and bandwidth usage Battery power and health (MacBooks only)... Read more
Cyberduck 4.6 - FTP and SFTP browser. (F...
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more
Maya 2015 - Professional 3D modeling and...
Maya is an award-winning software and powerful, integrated 3D modeling, animation, visual effects, and rendering solution. Because Maya is based on an open architecture, all your work can be scripted... Read more
Evernote 6.0.1 - Create searchable notes...
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at anytime, from... Read more
calibre 2.11 - Complete e-library manage...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital... Read more
Herald 5.0.1 - Notification plugin for M...
Note: Versions 2.1.3 (for OS X 10.7), 3.0.6 (for OS X 10.8), and 4.0.8 (for OS X 10.9) are no longer supported by the developer. Herald is a notification plugin for Mail.app, Apple's Mac OS X email... Read more
Firetask 3.7 - Innovative task managemen...
Firetask uniquely combines the advantages of classical priority-and-due-date-based task management with GTD. Stay focused and on top of your commitments - Firetask's "Today" view shows all relevant... Read more
TechTool Pro 7.0.6 - Hard drive and syst...
TechTool Pro is now 7, and this is the most advanced version of the acclaimed Macintosh troubleshooting utility created in its 20-year history. Micromat has redeveloped TechTool Pro 7 to be fully 64... Read more
PhotoDesk 3.0.1 - Instagram client for p...
PhotoDesk lets you view, like, comment, and download Instagram pictures/videos! (NO Uploads! / Image Posting! Instagram forbids that! AND you *need* an *existing* Instagram account). But you can do... Read more
SuperDuper! 2.7.3 - Advanced disk clonin...
SuperDuper! is an advanced, yet easy to use disk copying program. It can, of course, make a straight copy, or "clone" -- useful when you want to move all your data from one machine to another, or do... Read more

Latest Forum Discussions

See All

Ubisoft Gives Everyone Two New Ways to E...
Ubisoft Gives Everyone Two New Ways to Earn In-Game Stuff for Far Cry 4 Posted by Jessica Fisher on November 21st, 2014 [ permalink ] | Read more »
Golfinity – Tips, Tricks, Strategies, an...
Dig this: Would you like to know what we thought of being an infinite golfer? Check out our Golfinity review! Golfinity offers unlimited ways to test your skills at golf. Here are a few ways to make sure your score doesn’t get too high and your... | Read more »
Dark Hearts, The Sequel to Haunting Meli...
Dark Hearts, The Sequel to Haunting Melissa, is Available Now Posted by Jessica Fisher on November 21st, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Meowza! Toyze Brings Talking Tom to Life...
Meowza! | Read more »
Square Enix Announces New Tactical RPG f...
Square Enix Announces New Tactical RPG for Mobile, Heavenstrike Rivals. Posted by Jessica Fisher on November 21st, 2014 [ permalink ] With their epic stories and gorgeous graphics, | Read more »
Quest for Revenge (Games)
Quest for Revenge 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: The great Kingdom of the west has fallen. The gods ignore the prayers of the desperate. A dark warlord has extinguished... | Read more »
Threadz is a New Writing Adventure for Y...
Threadz is a New Writing Adventure for You and Your Friends Posted by Jessica Fisher on November 21st, 2014 [ permalink ] In the tradition of round-robin storytelling, | Read more »
SteelSeries Stratus XL Hardware Review
Made by: SteelSeries Price: $59.99 Hardware/iOS Integration Rating: 4 out of 5 stars Usability Rating: 4.5 out of 5 stars Reuse Value Rating: 4.25 out of 5 stars Build Quality Rating: 4.5 out of 5 stars Overall Rating: 4.31 out of 5 stars | Read more »
ACDSee (Photography)
ACDSee 1.0.0 Device: iOS iPhone Category: Photography Price: $1.99, Version: 1.0.0 (iTunes) Description: Capture, perfect, and share your photos with ACDSee. The ACDSee iPhone app combines an innovative camera, a powerful photo... | Read more »
ProTube for YouTube (Entertainment)
ProTube for YouTube 2.0.2 Device: iOS Universal Category: Entertainment Price: $1.99, Version: 2.0.2 (iTunes) Description: ProTube is the ultimate, fully featured YouTube app. With it's highly polished design, ProTube offers ad-free... | Read more »

Price Scanner via MacPrices.net

New 13-inch 1.4GHz MacBook Air on sale for $8...
 Adorama has the 2014 13″ 1.4GHz/128GB MacBook Air on sale for $899.99 including free shipping plus NY & NJ tax only. Their price is $100 off MSRP. B&H Photo has the 13″ 1.4GHz/128GB MacBook... Read more
Apple Expected to Reverse Nine-Month Tablet S...
Apple and Samsung combined accounted for 62 percent of the nearly 36 million branded tablets shipped in 3Q 2014, according to early vendor shipment share estimates from market intelligence firm ABI... Read more
Stratos: 30 Percent of US Smartphone Owners t...
Stratos, Inc., creator of the Bluetooth Connected Card Platform, has announced results from its 2014 Holiday Mobile Payments Survey. The consumer survey found that nearly one out of three (30 percent... Read more
2014 1.4GHz Mac mini on sale for $449, save $...
 B&H Photo has lowered their price on the new 1.4GHz Mac mini to $449.99 including free shipping plus NY tax only. Their price is $50 off MSRP, and it’s the lowest price available for this new... Read more
64GB iPod touch on sale for $249, save $50
Best Buy has the 64GB iPod touch on sale for $249 on their online store for a limited time. Their price is $50 off MSRP. Choose free shipping or free local store pickup (if available). Sale price for... Read more
15″ 2.2GHz Retina MacBook Pro on sale for $17...
 B&H Photo has the 2014 15″ 2.2GHz Retina MacBook Pro on sale for $1799.99 for a limited time. Shipping is free, and B&H charges NY sales tax only. B&H will also include free copies of... Read more
New Logitech AnyAngle Case/Stand Brings Flexi...
Logitec has announced the newest addition to its suite of tablet products — the Logitech AnyAngle. A protective case with an any-angle stand for iPad Air 2 and all iPad mini models, AnyAngle is the... Read more
2013 15-inch 2.0GHz Retina MacBook Pro availa...
B&H Photo has leftover previous-generation 15″ 2.0GHz Retina MacBook Pros available for $1499 including free shipping plus NY sales tax only. Their price is $500 off original MSRP. B&H will... Read more
16GB Retina iPad mini on sale today for $199,...
 Staples has 2nd generation 16GB Retina iPad minis on sale for $199 on their online store for a limited time. Their price is $100 off MSRP. Choose free shipping or free local store pickup (if... Read more
Developers Start Designing Apps for Apple Wat...
Apple has announced the availability of WatchKit, software that gives developers a set of tools to easily create experiences designed specifically for Apple Watch. Apple’s developer community can now... Read more

Jobs Board

*Apple* Solutions Consultant (ASC)- Retail S...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Project Manager, *Apple* Financial Services...
**Job Summary** Apple Financial Services (AFS) offers consumers, businesses and educational institutions ways to finance Apple purchases. We work with national and Read more
*Apple* Store Leader Program - College Gradu...
Job Description: Job Summary As an Apple Store Leader Program agent, you can continue your education as you major in the art of leadership at the Apple Store. You'll Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.