meta_query 是元子句的数组。例如：

$q = new WP_Query( array(
    \'meta_query\' => array(
        \'relation\' => \'AND\',
        array(
            \'key\' => \'state\',
            \'value\' => \'Wisconsin\',
        ),
        array(
            \'key\' => \'city\',
            \'compare\' => \'EXISTS\',
        ), 
    ),
) );

可以使用关联数组，每个meta子句都有一个键：

$q = new WP_Query( array(
    \'meta_query\' => array(
        \'relation\' => \'AND\',
        \'state_clause\' => array(
            \'key\' => \'state\',
            \'value\' => \'Wisconsin\',
        ),
        \'city_clause\' => array(
            \'key\' => \'city\',
            \'compare\' => \'EXISTS\',
        ), 
    ),
) );

然后，您可以在order_by 参数，带一个：

$q = new WP_Query( array(
    \'meta_query\' => array(
        \'relation\' => \'AND\',
        \'state_clause\' => array(
            \'key\' => \'state\',
            \'value\' => \'Wisconsin\',
        ),
        \'city_clause\' => array(
            \'key\' => \'city\',
            \'compare\' => \'EXISTS\',
        ), 
    ),
    \'orderby\' => \'city_clause\', // Results will be ordered by \'city\' meta values.
) );

或更多条款：

$q = new WP_Query( array(
    \'meta_query\' => array(
        \'relation\' => \'AND\',
        \'state_clause\' => array(
            \'key\' => \'state\',
            \'value\' => \'Wisconsin\',
        ),
        \'city_clause\' => array(
            \'key\' => \'city\',
            \'compare\' => \'EXISTS\',
        ), 
    ),
    \'orderby\' => array( 
        \'city_clause\' => \'ASC\',
        \'state_clause\' => \'DESC\',
    ),
) );

示例取自this post 在Make WordPres核心博客中。