Create a subquery in PostgreSQL

postgresql_subquery.sql

/**
 * comments
 *     author
 *     comment_text
 *     created_at
 **/
SELECT author, created_at FROM 
    (SELECT  * FROM comments WHERE (created_at >= NOW() - interval '6 month') 
    ORDER BY created_at DESC LIMIT 100) subquery 
ORDER BY author ASC;