WordPress: OrderBY meta_key_value including null value

Question

I am trying to make a simple query in wordpress ordered by a meta_value_num of a custom field.

$args1 = array(
'post_type'         => 'task',
'post_status'       => 'publish',
'meta_key'          => 'task_due_date',  
'orderby'           => 'meta_value_num', 
'order'             => ASC, 
'posts_per_page'    => -1,                                                              
);

I want to include the posts that have the custom field empty or null too ordered first or last in the query. How can I achieve that?

Answer 1

A simple and quick solution:

<?php
setup_postdata( $GLOBALS['post'] =& $post );

$posts= get_posts(array(
    'post_type'         => 'task',
    'post_status'       => 'publish',
    'meta_key'          => 'task_due_date',  
    'orderby'           => 'meta_value_num', 
    'order'             => ASC, 
    'posts_per_page'    => -1,                                                              
    ));

if( $posts ):
    foreach( $posts as $post ): ?>      

    <!-- HTML HERE -->

    <?php endforeach;
    wp_reset_postdata();
endif; ?>
?>

If you want to get the generated SQL just pass it to the WP_Meta_Query object:

$query_args = array(
    'post_type'         => 'task',
    'post_status'       => 'publish',
    'meta_key'          => 'task_due_date',  
    'orderby'           => 'meta_value_num', 
    'order'             => ASC, 
    'posts_per_page'    => -1,                                                              
    );

$meta_query = new WP_Meta_Query();
$meta_query->parse_query_vars( $query_args );
$res = $meta_query->get_sql(
    'task',
    $wpdb->posts,
    'ID',
    null
);