Filter post query results by one one post-meta value; sort results by another post-meta value.

wp-sort-limit-meta.php

<?php
/**
 * Sort query results by one meta value; filter by another.
 * For example, post are 'cities': 
 * Sort cities with >40K population ('city_pop') by average income ('city_income').
 */
$args = array(
    'post_type'      => 'cities',
    'posts_per_page' => 1000,
    'meta_query' => array(
        'relation' => 'AND',
        array(
        'population' => array( // Name this array key to use in 'onderby' below in ).
            'key' => 'city_pop', // Sort results by values with this meta key.
            'compare' => 'EXIST'
            )
        ),
        array(
            'key'     => 'city_income', // Filter results by values in this meta_key.
            'value'   => 40000, // Limits resutls to >40K. Uses 'compare' below.
            'type'    => 'numeric',
            'compare' => '>',
        )
    ),
    'orderby' => array( 'population' => 'DESC', 'title' => 'ASC' ), // Named array key from above.
);
$query_sort_limit = new WP_Query( $args );

// Make array of Publications data.
foreach ( $query_sort_limit->posts as $post ) {
    // Do stuff.
}
?>