PHP Functions for Retrieving Metadata

The most complete way to retrieve metadata is by using a SELECT statement against the
INFORMATION_SCHEMA database in the MySQL server. However, there are times that is overkill for
the data needing to be collected for a PHP application. With that said, PHP offers multiple functions that
provide methods for retrieving a small amount of metadata about the data in the MySQL server.

Database Metadata

The mysql_list_dbs() function retrieves the name of all the databases found on the server that are
accessible by the user requesting the information:

<?php
// Load variables used in mysql_connect and connect to server
include "connect_info.php";
$linkID1 = mysql_connect($dbhost,$dbuser,$dbpass) or
die("Could not connect to MySQL server");
// Retrieve the names of the databases accessible by the user
$schema_results = mysql_list_dbs($linkID1);
print "The databases available to the root user are: \n";
while (list($schema) = mysql_fetch_row($schema_results)) {
print "$schema \n";
}
// mysql_db_name() also displays the databases
print "The databases available to the root user are: \n";
for ($count=0; $count < mysql_num_rows($schema_results); $count++) {
print mysql_db_name($schema_results,$count)." \n";
}
?>

Table Metadata

The mysql_list_tables()function retrieves the name of all the tables found in the database identified that are
accessible by the user requesting the information:

<?php
// Load variables used in mysql_connect and connect to server
include "connect_info.php";
$linkID1 = mysql_connect($dbhost,$dbuser,$dbpass) or
die("Could not connect to MySQL server");
// List world database tables accessible by the user
$table_results = mysql_list_tables('world',$linkID1);
print "The world database tables available to the root user are: \n";
while (list($table) = mysql_fetch_row($table_results)) {
print "$table \n";
}
// mysql_tablename() also displays the world database tables retrieved
print "The world database tables available to the root user are: \n";
for ($count=0; $count < mysql_num_rows($table_results); $count++) {
print mysql_tablename($table_results,$count)." \n";
}
?>

PHP INTRODUCTION

PHP (recursive acronym for PHP: Hypertext Preprocessor ) is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML. PHP stands for P HP: H ypertext P reprocessor PHP is a server-side scripting language, like ASP PHP scripts are executed on the server PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, Generic ODBC, etc.) PHP is an open source software PHP is free to download and use Why PHP? PHP runs on different platforms (Windows, Linux, Unix, etc.) PHP is compatible with almost all servers used today (Apache, IIS, etc.) PHP is FREE to download from the official PHP resource: www.php.net PHP is easy to learn and runs efficiently on the server side What can PHP do? Anything. PHP is mainly focused on server-side scripting, so you can...

Storage Engine Breakdown

The following diagram represents a simplified view of the MySQL server and its interaction with the storage engines. The following properties are storage engine dependant: • Storage Medium – Each table uses its own method of storing the data it contains. • Transactional Capabilities – Certain storage engines handle transactional processing which ensures that integrity of a database is maintained during the processing of multiple SQL statements.

Outer Joins

Whereas an INNER JOIN will find combinations of matching rows from joined tables, the OUTER JOIN also finds the instances where a row in one table has no match in another table. An OUTER JOIN find matches (just like an INNER JOIN), but also identifies mismatches. Two forms of outer joins are LEFT JOIN and RIGHT JOIN . These do not use the comma separator or the INNER JOIN keywords. They each answer the same kinds of questions, but differ slightly in their syntax. That is a LEFT JOIN can always be re-written into a equivalent RIGHT JOIN. (In the following sections, the terms left table and right table refer to the tables named first and second in the FROM clause, respectively.) Left Outer Join A left join is a type of outer join, written using the LEFT JOIN keywords. A left join treats the left table (the first one named) as a reference table and produces output for each row selected from it, whether or not the row is matched by rows in the right table. Like a join w...

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