Wordpress Plugin with Database connection

I am using WordPress Version 2.9.2 for my blog.when i am trying to include a database connection in one of my plug-in which is not working properly.Which did not get the database connection.But in all other directory it is possible to use a c开发者_运维技巧ommon connection.So,now I am using manual coding in all of my plug-in file.Any ways to getting a common connection in all of my plug-in.Help me please...

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you should study more about wordpress

eg:

<?php
$table = "wp_table";
$data = $wpdb->get_results("SELECT * FROM $table WHERE 1=1", ARRAY_A);
?>

this a common connection