Interfacing Relational Databases to the Web
To change field values in records, use UPDATE:
UPDATE tablename SET field-1 = value-n WHERE qualification
The WHERE is optional, but if you don't specify a WHERE clause, SQL will update all the records, which is clearly the “Wrong Thing”.
Let's say Fred Mbogo wants to change his shell. This script will do it:
UPDATE passwd SET shell = '/bin/tcsh' WHERE username = 'fred';
To delete records, simply use DELETE:
DELETE FROM tablename WHERE qualifier
Just like UPDATE, the WHERE is optional, but you probably want it anyway. Let's say Fred has offended his sysadmin one too many times:
DELETE FROM passwd WHERE username = 'fred';
The on-line PHP3 manual, http://www.php.net/manual/, is an excellent reference and will be necessary reading before you create your own database web application. Furthermore, it is a database-backed web site and has lots of user comments. Here, we will examine just the most basic PHP3 features.
Here is a simple PHP3 program, which demonstrates some basic features. Note the separate HTML and PHP3 blocks:
<title>Hello, world!</title> <body> <?php echo("Hello, world!\n"); echo("<p>\nWhat a <b>bold</b> move this is!\n"); ?> </body>
This program will send the following HTML to the remote browser:
<title>Hello, world!</title> <body> Hello, world! <p> What a <b>bold</b> move this is! </body>A similar program, which takes an argument, would look like this:
<title>Hello, world!</title> <body> <?php echo("Hello, $name!\n"); echo("<p>\nWhat a <b>bold</b> move this is!\n"); ?> </body>You would view this page (assuming you called it hello.php3) like any CGI script: http://yourhost.net/~fred/hello.php3?name=fred. This, of course, assumes you are named Fred and have put this file in your /public_html directory.
PHP3 provides a number of useful functions for connecting to databases; the best place to read up on these is www.php.net/manual/ref.pgsql.php3, and we shall examine a few of them.
int pg_connect(host, port, options, tty, dbname);
This function returns an integer, the “connection index”, which you will need for all operations on this connection. If a connection can't be established, it returns zero.
int pg_exec(conn, query); Executes the SQL query query on connection conn. Returns a result set index.
int pg_numrows(result); Returns the number of tuples in the result set result.
array pg_fetch_row(result,Returns an array of values corresponding to the row row of result set result.
void pg_close(conn); Closes the connection conn.
Our example application is an address book that one can access over the Internet. A user logs in with her name and password and is presented with a menu of options, including browsing and searching the address book and adding a new person. For each person in the address book, the database stores an arbitrary number of e-mail addresses, telephone numbers, URLs and postal addresses. This address book also has some nifty features like mailing passwords to new accounts and automatic mailto and href links for e-mail and web addresses.
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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|The Firebird Project's Firebird Relational Database||Jul 29, 2016|
|Stunnel Security for Oracle||Jul 28, 2016|
|SUSE LLC's SUSE Manager||Jul 21, 2016|
|My +1 Sword of Productivity||Jul 20, 2016|
|Non-Linux FOSS: Caffeine!||Jul 19, 2016|
|Murat Yener and Onur Dundar's Expert Android Studio (Wrox)||Jul 18, 2016|
- Stunnel Security for Oracle
- The Firebird Project's Firebird Relational Database
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- SUSE LLC's SUSE Manager
- Managing Linux Using Puppet
- My +1 Sword of Productivity
- Non-Linux FOSS: Caffeine!
- SuperTuxKart 0.9.2 Released
- Google's SwiftShader Released
- Doing for User Space What We Did for Kernel Space
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide