PostgreSQL、集約関数でカラムエイリアスにhavingは使えない？

PostgreSQL、集約関数でカラムエイリアスにhavingは使えないっぽい

例）商品テーブル（products）からcategory_idごとの商品の合計値段から、合計値段が1000を越えるcategory_idを抽出

• NG:

select category_id, sum(price) as amount from products group by category_id having amount > 1000

• OK:

select category_id, sum(price) from products group by category_id having sum(price) > 1000