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

Alfred 2.6 - 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
1Password 5.1 - Powerful password manage...
1Password is a password manager that uniquely brings you both security and convenience. It is the only program that provides anti-phishing protection and goes beyond password management by adding Web... Read more
GarageSale 6.9.2 - Create outstanding eB...
GarageSale is a slick, full-featured client application for the eBay online auction system. Create and manage your auctions with ease. With GarageSale, you can create, edit, track, and manage... Read more
calibre 2.17 - 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 librarian... Read more
OmniGraffle Pro 6.1.2 - Create diagrams,...
OmniGraffle Pro helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use... Read more
OmniGraffle 6.1.2 - Create diagrams, flo...
OmniGraffle helps you draw beautiful diagrams, family trees, flow charts, org charts, layouts, and (mathematically speaking) any other directed or non-directed graphs. We've had people use Graffle to... Read more
RoboForm 2.0.2 - Password manager; syncs...
RoboForm is a password manager that offers one-click login, mobile syncing, easy form filling, and reliable security. Password Manager. RoboForm remembers your passwords so you don't have to! Just... Read more
Apple MainStage 3.1 - Live performance t...
Love the sound you got on your recording? MainStage 3 makes it easy to bring all the same instruments and effects to the stage. Everything from the Sound Library and Smart Controls you're familiar... Read more
Freeway Pro 7.0.2 - Drag-and-drop Web de...
Freeway Pro lets you build websites with speed and precision... without writing a line of code! With its user-oriented drag-and-drop interface, Freeway Pro helps you piece together the website of... Read more
A Better Finder Rename 9.44 - File, phot...
A Better Finder Rename is the most complete renaming solution available on the market today. That's why, since 1996, tens of thousands of hobbyists, professionals and businesses depend on A Better... Read more

This Week at 148Apps: January 19-23, 201...
Warm Your Winter With New Apps!   How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you’re looking for. The ones we love become Editor’s Choice, standing out... | Read more »
Eggmaster Review
Eggmaster Review By Jennifer Allen on January 26th, 2015 Our Rating: :: BRIEFLY COMPELLINGUniversal App - Designed for iPhone and iPad Tap like crazy to gain eggs, so that you can buy upgrades to gain more eggs, and so on. It... | Read more »
Cloudy Or Dry – Funny Or Die Release a W...
Cloudy Or Dry – Funny Or Die Release a Weather App Posted by Ellis Spice on January 26th, 2015 [ permalink ] iPhone App - Designed for the iPhone, compatible with the iPad | Read more »
Mediocre, the Team Behind Smash Hit, is...
Mediocre, the Team Behind Smash Hit, is Teasing Their Latest Unnamed Project Posted by Jessica Fisher on January 26th, 2015 [ permalink ] | Read more »
Heroes of Gaia Review
Heroes of Gaia Review By Campbell Bird on January 26th, 2015 Our Rating: :: TIMERS OF MIGHT AND MAGICUniversal App - Designed for iPhone and iPad This free-to-play rpg looks a lot like Heroes of Might and Magic, but it’s poor... | Read more »
Choice Provisions is Set to Launch Destr...
Choice Provisions is Set to Launch Destructamundo on iOS This Month Posted by Tre Lawrence on January 23rd, 2015 [ permalink ] Choice Provisions – home stable to | Read more »
King of Thieves – An Interview With Zept...
Ahead of the release of ZeptoLab’s King of Thieves, we were able to ask ZeptoLab’s co-founder, Semyon Voinov, a few questions about the inspiration behind the game and what that means for the Cut the Rope franchise. | Read more »
Handle Review
Handle Review By Jennifer Allen on January 23rd, 2015 Our Rating: :: SPEEDY ORGANIZINGUniversal App - Designed for iPhone and iPad Handle is a very convenient way of juggling your emails, To Do list, and Calendar all through one... | Read more »
The New Disney Inquizitive App Offers a...
The New Disney Inquizitive App Offers a Place for Fans to Take Disney Quizzes Posted by Tre Lawrence on January 23rd, 2015 [ permalink ] | Read more »
Hands-On With Cut the Rope Developer Zep...
Marking quite a departure from ZeptoLab’s past successes, namely the Cut The Rope series, King of Thieves is shaping up to be quite promising. Due for release in February, we were lucky enough to have some time with a preview build to see exactly... | Read more »

Price Scanner via MacPrices.net

MasterCard Brings Contactless Payment, Apple...
MasterCard, the official card of the Waste Management Phoenix Open, and the PGA TOUR are bringing the latest payment technology to the spectator experience with the introduction of contactless... Read more
Petitioning Dropbox For Mac OS X 10.4 and 10....
Last week Dropbox announced to its users that app support for Mac OS X 10.4 and 10.5 will end May 18 — disappointing news for those of us who are still getting useful service out of older PPC Macs... Read more
Stop Street Harassment, Bullying, and Assault...
The STOP-ATTACK (http://www.stop-attack.com) app will leverage smartphone technology to make the world a safer place. Whether it’s bullying, street harassment or something even more sinister, the app... Read more
Stir Kinetic Desk M1 Standing Or Sitting Desk...
The age of the standing desk is upon us, and according to medical research, it’s arriving none too soon. The World Health Organization (WHO), reports that 60 to 85 percent of people worldwide lead... Read more
Bosch Opens North American eBike Conversion H...
Following its entry into the U.S. eBike market in early 2014, Bosch has established a new headquarters office for Bosch eBike Systems (http://www.bosch-ebike.us) in Southern California, expanding the... Read more
13-inch 2.4GHz Retina MacBook Pro (Apple refu...
The Apple Store has previous-generation Apple Certified Refurbished 13″ 2.4GHz/128GB Retina MacBook Pros available for $999. Apple’s one-year warranty is standard, and shipping is free: - 13″ 2.4GHz/... Read more
13-inch 2.6GHz Retina MacBook Pro on sale for...
Adorama has the 13″ 2.6GHz/128GB Retina MacBook Pro on sale for $1189.99, $110 off MSRP. Shipping is free, and Adorama charges NY & NJ sales tax only. Read more
College Student Deals are back, additional $5...
Take an additional $50 off all MacBooks and iMacs at Best Buy Online with their College Students Deals Savings, valid through April 11, 2015. Anyone with a valid .EDU email address can take advantage... Read more
iPhone 6 and 6 Plus GIve Apple Half Of US Mob...
Chicago-based Consumer Intelligence Research Partners, LLC (CIRP) have released analysis of the results of its research on mobile phone manufacturers for the calendar quarter that ended December 31,... Read more
Save $100 on MacBook Airs with 256GB of stora...
B&H Photo has 256GB MacBook Airs on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 1.4GHz/256GB MacBook Air: $999 $100 off MSRP - 13″ 1.4GHz/256GB MacBook... Read more

Jobs Board

Detailer *Apple* Ford Body Shop / Collision...
Apple Automotive is one of the fastest growing dealer…and it shows. Consider making the switch to the Apple Automotive Group today! At Apple Automotive , Read more
*Apple* Acura/Subaru Service Technicians - A...
Apple Automotive is one of the fastest growing dealer…and it shows. Consider making the switch to the Apple Automotive Group today! At Apple Automotive , Read more
Business Development Manager - *Apple* Pay...
**Job Summary** Apple Pay is seeking an experienced business development manager to support the identification, recruitment, negotiation and ongoing management of Read more
*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
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.