PostgreSQLでは副問い合わせ(subquery)に別名を付けないと怒られたメモ - Qiita

SELECT 年月, SUM(販売金額) AS 販売合計金額 FROM ( SELECT TO_CHAR(s.sale_date, 'yyyy-mm') AS 年月, s.quantity * p.price AS 販売金額 FROM sales AS s JOIN products AS p ON s.product_id = p.product_id ) GROUP BY 年月 ORDER BY 年月 ; ---------------------------------------------------- db_name=# 上記SQL文 ERROR: subquery in FROM must have an alias LINE 1: select 年月, sum(販売金額) as 販売合計金額 from (select TO_C... ^ HINT: For example,