用一个简单的查询不可能得到每个类别一篇文章，甚至一个复杂的查询也需要比3个单独的查询更多的时间。所以，如果你想要最简单的，那么这就是解决方案-

$cats = array(\'lifestyle\', \'fashion\', \'beauty\');
$exclude_posts = array();
foreach( $cats as $cat )
{
    // build query argument
    $query_args = array(
        \'category_name\' => $cat,
        \'showposts\' => 1,
        \'post_type\' => \'post\',
        \'post_status\' => \'publish\',
        \'orderby\' => \'date\',
        \'order\' => \'DESC\'
    );

    // exclude post that already have been fetched
    // this would be useful if multiple category is assigned for same post
    if( !empty($exclude_posts) )
        $query_args[\'post__not_in\'] = $exclude_posts;

    // do query
    $query = new WP_Query( $query_args );

    // check if query have any post
    if ( $query->have_posts() ) {

        // start loop
        while ( $query->have_posts() ) {
            // set post global
            $query->the_post();

            // add current post id to exclusion array
            $exclude_posts[] = get_the_ID();


            // do something
        }
    } else {
        // no posts found
    }

    // Restore original Post Data
    wp_reset_postdata();
}