WP_Tax_Query example

function get_tax_sql( $tax_query, $primary_table, $primary_id_column ) {
    $tax_query_obj = new WP_Tax_Query( $tax_query );
    return $tax_query_obj->get_sql( $primary_table, $primary_id_column );
}

/** * Gets all term data from database by term ID. * * The usage of the get_term function is to apply filters to a term object. It * is possible to get a term object from the database before applying the * filters. * * $term ID must be part of $taxonomy, to get from the database. Failure, might * be able to be captured by the hooks. Failure would be the same value as $wpdb * returns for the get_row method. * * There are two hooks, one is specifically for each term, named 'get_term', and * the second is for the taxonomy name, 'term_$taxonomy'. Both hooks gets the * term object, and the taxonomy name as parameters. Both hooks are expected to * return a term object. * * {@see 'get_term'} hook - Takes two parameters the term Object and the taxonomy name. * Must return term object. Used in get_term() as a catch-all filter for every * $term. * * {@see 'get_$taxonomy'} hook - Takes two parameters the term Object and the taxonomy * name. Must return term object. $taxonomy will be the taxonomy name, so for * example, if 'category', it would be 'get_category' as the filter name. Useful * for custom taxonomies or plugging into default taxonomies. * * @todo Better formatting for DocBlock * * @since 2.3.0 * @since 4.4.0 Converted to return a WP_Term object if `$output` is `OBJECT`. * The `$taxonomy` parameter was made optional. * * @see sanitize_term_field() The $context param lists the available values for get_term_by() $filter param. * * @param int|WP_Term|object $term If integer, term data will be fetched from the database, * or from the cache if available. * If stdClass object (as in the results of a database query), * will apply filters and return a `WP_Term` object with the `$term` data. * If `WP_Term`, will return `$term`. * @param string $taxonomy Optional. Taxonomy name that `$term` is part of. * @param string $output Optional. The required return type. One of OBJECT, ARRAY_A, or ARRAY_N, which * correspond to a WP_Term object, an associative array, or a numeric array, * respectively. Default OBJECT. * @param string $filter Optional. How to sanitize term fields. Default 'raw'. * @return WP_Term|array|WP_Error|null WP_Term instance (or array) on success, depending on the `$output` value. * WP_Error if `$taxonomy` does not exist. Null for miscellaneous failure. */

if ( ! empty( $q['tag_slug__and'] ) ) {
            $q['tag_slug__and'] = array_map( 'sanitize_title_for_query', array_unique( (array) $q['tag_slug__and'] ) );
            $tax_query[]        = array(
                'taxonomy' => 'post_tag',
                'terms'    => $q['tag_slug__and'],
                'field'    => 'slug',
                'operator' => 'AND',
            );
        }

        $this->tax_query = new WP_Tax_Query( $tax_query );

        /** * Fires after taxonomy-related query vars have been parsed. * * @since 3.7.0 * * @param WP_Query $query The WP_Query instance. */
        do_action( 'parse_tax_query', $this );
    }