YOUR WEBSITE

The INFORMATION_SCHEMA is a virtual database that is automatically created and populated by MySQL, there is no need to create an INFORMATION_SCHEMA database. There also is no associated file structure due to the fact that the contents of the data are actual views, rather than logical data being stored in any one location. Only SELECT statements are allowed against the tables in the INFORMATION_SCHEMA database. The following SELECT example demonstrates some of the metadata that can be viewed: <?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"); // Execute Query to Collect Metadata $query = "SELECT TABLE_NAME, ENGINE, TABLE_ROWS, UPDATE_TIME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA='world'"; $results = mysql_query($query, $linkID1); // Build HTML Table of Results print "<table

              When tables are joined, it's often the case that the tables contain columns with the same names. If such a column is referred to in the query, it's ambiguous which table the column reference applies to. This ambiguity usually can be addressed by qualifying column names with table names. However, if a join is on a table to itself, even the table name is ambiguous and it's necessary to use aliases to disambiguate table references. This section describes how to address naming issues in queries by qualifying column and table names and by using aliases. Qualifying Column Names                If a column name used in the query appears in more than one table, the name is ambiguous and it's necessary to provide information that identifies which table the column is connected to. This has been accommplished by qualifying the column name with the appropriate table name throughout the examples in this chapter. If name qualification has not been used, then pro