14. 少し複雑なクエリ 鍵付きユーザーの「いいね」について名前を 「匿名」にして出している WITH comments AS ( SELECT comments.id, content, users.name AS user_name, comments.created_at FROM comments JOIN users ON comments.user_id = users.id ), likes AS ( SELECT COALESCE(users.name, '匿名') AS user_name, likes.created_at, comment_id FROM likes LEFT OUTER JOIN users ON likes.user_id = users.id ) SELECT comments.id, content, comments.user_name ,