How to get all post data from wordpress using custom query

get all post using custom or select query using following code
<?php
 $querystr = "
    SELECT $wpdb->posts.*
    FROM $wpdb->posts, $wpdb->postmeta
    WHERE $wpdb->posts.ID = $wpdb->postmeta.post_id
    AND $wpdb->postmeta.meta_key = 'tag'
    AND $wpdb->postmeta.meta_value = 'email'
    AND $wpdb->posts.post_status = 'publish'
    AND $wpdb->posts.post_type = 'post'
    AND $wpdb->posts.post_date < NOW()
    ORDER BY $wpdb->posts.post_date DESC
 ";



 $pageposts = $wpdb->get_results($querystr, OBJECT);

 ?>

for more reference visit this site : http://codex.wordpress.org/Displaying_Posts_Using_a_Custom_Select_Query