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.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

OmniOutliner Pro 4.6 - Pro version of th...
OmniOutliner Pro is a flexible program for creating, collecting, and organizing information. Give your creativity a kick start by using an application that's actually designed to help you think. It's... Read more
Alfred 3.1 - Quick launcher for apps and...
Alfred is an award-winning productivity application for OS X. Alfred saves you time when you search for files online or on your Mac. Be more productive with hotkeys, keywords, and file actions at... Read more
OmniOutliner 4.6 - Organize your ideas,...
OmniOutliner is a flexible program for creating, collecting, and organizing information. Give your creativity a kick start by using an application that's actually designed to help you think. It's... Read more
Default Folder X 5.0.6 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more
Adobe Creative Cloud 3.8.0.310 - Access...
Adobe Creative Cloud costs $19.99/month for a single app, or $49.99/month for the entire suite. Introducing Adobe Creative Cloud desktop applications, including Adobe Photoshop CC and Illustrator CC... Read more
MYStuff Pro 2.0.25 - Create inventories...
MYStuff Pro is the most flexible way to create detail-rich inventories for your home or small business. Add items to MYStuff by dragging and dropping existing information, uploading new images, or... Read more
Viber 6.2.0 - Send messages and make cal...
Viber lets you send free messages and make free calls to other Viber users, on any device and network, in any country! Viber syncs your contacts, messages and call history with your mobile device, so... Read more
Data Rescue 4.2.3 - Powerful hard drive...
Use Data Rescue to recover: crashed, corrupted or non-mounting hard drive deleted, damaged, or lost files reformatted or erased hard drive One powerful new feature found in Data Rescue 4 is... Read more
Microsoft Remote Desktop 8.0.34 - Connec...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more
Microsoft Remote Desktop 8.0.34 - Connec...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more

Find out the story behind League of Ange...
If you’re looking for a new thrilling MMORPG to play with your friends then you’ll be excited to hear that there is a sequel to one of the most well known titles in the genre – namely League of Angels 2. With a brand new 3D engine offering... | Read more »
Naruto Shippuden: Ultimate Ninja Blazing...
I'm not sure if it's possible to say you are an anime fan but also never have seen one episode of Naruto. If it is, then I resemble that remark, and if not, I offer a hearty apology. [Read more] | Read more »
5 mobile games that let you explore spac...
No Man's Sky hasn't exactly turned out to be everything it was promised. Though its core concept of exploring an unimaginably vast universe of different planets is an intriguing one, the execution has left many PS4 and PC gamers feeling like they... | Read more »
Mummy madness in new action game Tomb He...
Hot on the tail of Bump Hero, ZPlay is giving gamers another reason to get screen bashing with a brand new release. Tomb Heroes is a challenging action game in which you battle enemies in various tombs around the world. You can select from nine... | Read more »
Siralim 2 (RPG / Roguelike) (Games)
Siralim 2 (RPG / Roguelike) 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Siralim 2 is an old-school monster catching RPG. Summon and customize hundreds of creatures to fight for you as... | Read more »
Clean Text (Productivity)
Clean Text 1.0 Device: iOS Universal Category: Productivity Price: $3.99, Version: 1.0 (iTunes) Description: | Read more »
Gemini - A Journey of Two Stars (Games)
Gemini - A Journey of Two Stars 1.0.1 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.1 (iTunes) Description: *** SPECIAL LAUNCH SALE: $2.99 (25% off) *** "A mesmerizing and unexpectedly emotional journey." -- Los... | Read more »
How to get four NFL superstars for your...
Even though you're probably well on your way to building a top notch squad for the new season in Madden NFL Mobile, let's say you could beef it up by adding Rob Gronkowski, Antonio Brown, Von Miller, and Todd Gurley to your roster. That's... | Read more »
Cartoon Network Superstar Soccer: Goal!!...
Cartoon Network Superstar Soccer: Goal!!! – Multiplayer Sports Game Starring Your Favorite Characters 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Become a soccer superstar with your... | Read more »
NFL Huddle: What's new in Topps NFL...
Can you smell that? It's the scent of pigskin in the air, which either means that cliches be damned, pigs are flying in your neck of the woods, or the new NFL season is right around the corner. [Read more] | Read more »

Price Scanner via MacPrices.net

RESCUECOM 2016 Semi-Annual Computer Reliabili...
The beginning of a new school year is upon us again, in which students and parents have some very important choices to make, often including the purchase of a computer or tablet. Whether you are... Read more
VRS Design Damda Glide Series iPhone 7 and 7...
What makes the Damda Glide Series for the iPhone 7 and iPhone 7 Plus special? Case maker VRS Design says its Damda Glide Series is the first mobile case to incorporate a semi-automatic mechanism for... Read more
Apple refurbished iMacs available for up to $...
Apple has Certified Refurbished 2015 21″ & 27″ iMacs available for up to $350 off MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are available: - 21″ 3.... Read more
Clearance 2015 13-inch MacBook Airs available...
B&H Photo has clearance 2015 13″ MacBook Airs available for $350 off original MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 1.6GHz/4GB/128GB MacBook Air (MJVE2LL/A): $829... Read more
Check Apple prices on any device with the iTr...
MacPrices is proud to offer readers a free iOS app (iPhones, iPads, & iPod touch) and Android app (Google Play and Amazon App Store) called iTracx, which allows you to glance at today’s lowest... Read more
Save $120 with Apple refurbished Time Capsule...
Apple has certified refurbished Time Capsules available for $120 off MSRP. Apple’s one-year warranty is included with each Time Capsule, and shipping is free: - 2TB Time Capsule: $179, $120 off (not... Read more
9-inch 32GB iPad Pros on sale for $70 off MSR...
B&H Photo has 9″ 32GB WiFi Apple iPad Pros on sale for $70 off MSRP, each including free shipping. B&H charges sales tax in NY only: - 9″ Space Gray 32GB WiFi iPad Pro: $529 $70 off MSRP - 9... Read more
Mac minis on sale for up to $140 off MSRP
Adorama has Mac minis on sale for up to $100 off MSRP including free shipping plus NY & NJ sales tax only: - 1.4GHz Mac mini: $449 $50 off MSRP - 2.6GHz Mac mini: $649 $50 off MSRP Amazon has the... Read more
Back To School with OtterBox Essentials
Back to school means back to an environment that is tough on tech. OtterBox has the back to school essentials you need to keep tech safe from drops, bumps, scratches and hallway havoc. Check out the... Read more
VRS Design Releases New iPhone 7 Plus Case Li...
With a device as large and costly as the iPhone 7 Plus, it is primal instinct to protect it from potential damage. According to a study by SquareTrade in 2012, iPhone damages cost Americans roughly $... Read more

Jobs Board

*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 51218354 Fredericksburg, Virginia, United States Posted: Aug. 18, 2016 Weekly Hours: 40.00 **Job Summary** As an Apple Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* /Mac Support Engineer - GFI Digital,...
FI Digital, Inc. is currently seeking candidates for a full time Apple Support Engineer to add to our Maryland Heights, Missouri IT team. Candidates must be dynamic Read more
*Apple* Solutions Consultant - Apple (United...
Apple Solutions ConsultantJob Number: 51218534Pleasant Hill, California, United StatesPosted: Aug. 18, 2016Weekly Hours: 40.00Job SummaryAs an Apple Solutions Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 51443201 Mishawaka, Indiana, United States Posted: Aug. 25, 2016 Weekly Hours: 40.00 **Job Summary** As an Apple Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.