GROUP_CONCAT is a great way of grouping records and not lose variables that you’ll need later. For example; I have a table where magazines share the same title but some can be gifted and some can’t. By using GROUP_CONCAT I can keep track of how many magazines can be gifted.

The result I get from gGift will be the combined values from all the magazines that have the same Magazine name.

<?php if ( have_posts() ) the_post(); ?>
 <?php $term = get_term_by( 'slug', get_query_var( 'term' ),
 get_query_var( 'taxonomy' ) ); ?>
 <?php $tax = get_query_var( 'taxonomy' ); ?>

<h2><?php echo $term->name; ?></h2>

<?php rewind_posts(); ?>
 <?php global $post, $wp_query; ?>
 <?php $term = get_term_by( 'slug', get_query_var( 'term' ),
 get_query_var( 'taxonomy' ) ); ?>

<?php
 $args = array(
 'post_type' => 'products',
 $term->taxonomy => $term->slug,
 'meta_query' => array(
 array ('key' => 'product_start_date',
 'value' => date("Y-m-d"),
 'compare' => '<',
 'type' => 'NUMERIC,'),
 array ('key' => 'product_end_date',
 'value' => date("Y-m-d"),
 'compare' => '>',
 'type' => 'NUMERIC,'
 )
 ),
 'posts_per_page' => '-1',

);
 $temp = $wp_query;
 $wp_query = null;
 $wp_query = new WP_Query();
 $wp_query->query($args);

?>

<?php if ($wp_query->have_posts()) : ?>
 <?php while ($wp_query->have_posts()) : ?>
 <?php $wp_query->the_post(); ?>

post ...

<?php endwhile; ?>
 <?php endif; ?>

<?php $wp_query = null; $wp_query = $temp;?>

The first loop will display 1 post and will be checked against a start date, an end date and if the post is set as a featured post. The second loop is almost the same as the first loop, except that it will continue from where the first loop stops. The third loop will display the last added posts but will only display the posts if the start date is filled in correctly.

SELECT DISTINCT wposts.*
 FROM $wpdb->posts wposts,
 $wpdb->postmeta wpostmeta,
 $wpdb->postmeta wpostmeta2,
 $wpdb->postmeta wpostmeta3
 WHERE wposts.ID = wpostmeta.post_id
 AND wposts.ID = wpostmeta2.post_id
 AND wposts.ID = wpostmeta3.post_id
 AND wpostmeta.meta_key = 'product_featured'
 AND wpostmeta.meta_value = '1'
 AND wpostmeta2.meta_key = 'product_start_date'
 AND wpostmeta2.meta_value < '" . date("Y-m-d") . "'
 AND wpostmeta3.meta_key = 'product_end_date'
 AND wpostmeta3.meta_value > '" . date("Y-m-d") . "'
 AND wposts.post_type = 'products'
 AND wposts.post_status = 'publish'
 GROUP BY ID