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
$101.70
Apple Inc.
+0.84
MSFT
$46.56
Microsoft Corpora
-0.20
GOOG
$586.04
Google Inc.
+6.09

MacTech Search:
Community Search:

Software Updates via MacUpdate

Apple Digital Camera RAW Compatibility 5...
Apple Digital Camera RAW Compatibility update adds RAW image compatibility to Aperture 3 and iPhoto '11. For more information on supported RAW formats, see here.Version 5.07: Adds RAW camera... Read more
Transmit 4.4.7 - Excellent FTP/SFTP clie...
Transmit is an excellent FTP (file transfer protocol), SFTP, S3 (Amazon.com file hosting) and iDisk/WebDAV client that allows you to upload, download, and delete files over the internet. With the... Read more
Macgo Blu-ray Player 2.10.8.1715 - Blu-r...
Macgo Mac Blu-ray Player can bring you the most unforgettable Blu-ray experience on your Mac. Overview Macgo Mac Blu-ray Player can satisfy just about every need you could possibly have in a Blu-ray... Read more
Capture One Pro 8.0.0.433 - RAW workflow...
Capture One Pro 8 is a professional RAW converter offering you ultimate image quality with accurate colors and incredible detail from more than 300 high-end cameras -- straight out of the box. It... Read more
Adobe Acrobat Pro 11.0.09 - Powerful PDF...
Adobe Acrobat allows users to communicate and collaborate more effectively and securely. Unify a wide range of content in a single organized PDF Portfolio. Collaborate through electronic document... Read more
Adobe Reader 11.0.09 - View PDF document...
Adobe Reader allows users to view PDF documents. You may not know what a PDF file is, but you've probably come across one at some point. PDF files are used by companies and even the IRS to... Read more
iFFmpeg 4.6.1 - Convert multimedia files...
iFFmpeg is a graphical front-end for FFmpeg, a command-line tool used to convert multimedia files between formats. The command line instructions can be very hard to master/understand, so iFFmpeg does... Read more
NTFS 11.3.62 - Provides full read and wr...
Paragon NTFS breaks down the barriers between Windows and OS X. Paragon NTFS effectively solves the communication problems between the Mac system and NTFS, providing full read and write access to... Read more
OS X Yosemite 10.10 DP8 - Developer Prev...
Note: This is a Developer Preview. You must be a registered Apple Mac Developer to download this update. You can also sign up for the free OS X Beta Program to download and preview public beta... Read more
FotoMagico 4.5 - Powerful slideshow crea...
FotoMagico lets you create professional slideshows from your photos and music with just a few, simple mouse clicks. It sports a very clean and intuitive yet powerful user interface. High image... Read more

Latest Forum Discussions

See All

Little World Escape Review
Little World Escape Review By Jordan Minor on September 17th, 2014 Our Rating: :: EARTHBOUNDUniversal App - Designed for iPhone and iPad Little World Escape draws players in with captivating concepts before pushing them away with... | Read more »
Light in the Dark Review
Light in the Dark Review By Nadia Oxford on September 17th, 2014 Our Rating: :: LIGHT 'EM UP UP UPUniversal App - Designed for iPhone and iPad Light in the Dark is an interesting and challenging puzzle game with some amusing bits... | Read more »
ShareFile for iPad is iOS 8-Ready with N...
ShareFile for iPad is iOS 8-Ready with New File-Editi​ng Feature Posted by Jessica Fisher on September 17th, 2014 [ permalink ] | Read more »
Pizo Animals
Pizo Animals By Amy Solomon on September 17th, 2014 Our Rating: :: DELIGHTFUL PUZZLESUniversal App - Designed for iPhone and iPad Pizo Animals is a puzzle app that includes many options adults can choose to customize the experience... | Read more »
ETA for iOS 8 Introduces Today View Exte...
ETA for iOS 8 Introduces Today View Extension and is Having a 50% Off Sale Posted by Jessica Fisher on September 17th, 2014 [ permalink ] | Read more »
Get Ready to Hit the Ice – NHL 2K is Com...
Get Ready to Hit the Ice – NHL 2K is Coming to the App Store Soon Posted by Jessica Fisher on September 17th, 2014 [ permalink ] 2K announced today that they are bringing NHL 2K< | Read more »
Readdle Adds Tons of iOS 8 Updates for A...
Readdle Adds Tons of iOS 8 Updates for All Readdle Apps Posted by Jessica Fisher on September 17th, 2014 [ permalink ] With the iOS 8 dropping today, Readdle has dramatically | Read more »
Let it Rainbow Review
Let it Rainbow Review By Jennifer Allen on September 17th, 2014 Our Rating: :: SIMPLE COLORSiPhone App - Designed for the iPhone, compatible with the iPad A little too simple for extended sessions, Let It Rainbow is still a cute... | Read more »
Goat Simulator (Games)
Goat Simulator 1.0.1 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.1 (iTunes) Description: Goat Simulator is the latest in goat simulation technology, bringing next-gen goat simulation to YOU. You no longer have to... | Read more »
Almightree: The Last Dreamer Review
Almightree: The Last Dreamer Review By Blake Grundman on September 17th, 2014 Our Rating: :: CLIMBING HIGHERUniversal App - Designed for iPhone and iPad Can this Zelda-inspired platformer reach new heights of success?   | Read more »

Price Scanner via MacPrices.net

Logitech Bluetooth Multi-Device Cross-Platfor...
Logitech has an enviable track record of making some of the best computer keyboards and mice. At least in my estimation, the best freestanding keyboards I’ve ever used have been Logitech units,... Read more
Roundup of Apple refurbished iPad Airs and iP...
Apple is offering Certified Refurbished iPad Airs for up to $140 off MSRP. Apple’s one-year warranty is included with each model, and shipping is free. Stock tends to come and go with some of these... Read more
Sprint offers 16GB iPad mini for $199.99 with...
Sprint is offering 1st generation 16GB iPad minis for $199.99 with a 2-year service agreement. Standard MSRP for this iPad is $429. Their price is the lowest available for this model. Read more
2.5GHz Mac mini remains on sale for $549, sav...
B&H Photo has the 2.5GHz Mac mini on sale for $549.99 including free shipping. That’s $50 off MSRP, and B&H will also include a free copy of Parallels Desktop software. NY sales tax only. Read more
Apple refurbished iMacs available for up to $...
The Apple Store has Apple Certified Refurbished iMacs available for up to $300 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free. These are the best prices on... Read more
13″ 2.5GHz MacBook Pro offered for $100 off M...
B&H Photo has the 13″ 2.5GHz MacBook Pro on sale for $999.99 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
Free GIMP Professional Grade Graphics App Ver...
The latest 2.8.14 version of the oddly-named GIMP (acronym for: GNU Image Manipulation Program) open source, high-end image editing and creation alternative to Adobe’s Photoshop and refuge from... Read more
Apple Announces Record Pre-orders for iPhone...
Apple has released metrics showing a record number of first day pre-orders of iPhone 6 and iPhone 6 Plus, with over four million sold in the first 24 hours. Demand for the new iPhones exceeds the... Read more
10% off iPhone 6 and 6 Plus Otterbox cases
Get 10% off on popular Otterbox iPhone 6 and iPhone 6 Plus cases at MacMall through September 19th. Use code OTTERBOX10 to see the discount. Read more
15-inch MacBook Pros on sale for up to $125 o...
Amazon has the new 2014 15″ Retina MacBook Pros on sale for up to $125 off MSRP including free shipping: - 15″ 2.2GHz Retina MacBook Pro: $1899.99 save $100 - 15″ 2.5GHz Retina MacBook Pro: $2374... Read more

Jobs Board

*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
*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
*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
*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
*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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.