update titles set ytd_sales=ytd_sales+(select distinct s.qty from FROM titles t, sales s
WHERE t.title_id = s.title_id
AND s.ord_date = (SELECT MAX(sales.ord_date) FROM sales))
但是
select distinct s.qty from FROM titles t, sales s
WHERE t.title_id = s.title_id
AND s.ord_date = (SELECT MAX(sales.ord_date) FROM sales))
返回的必须是单个数据集才可以
WHERE t.title_id = s.title_id
AND s.ord_date = (SELECT MAX(sales.ord_date) FROM sales))
但是
select distinct s.qty from FROM titles t, sales s
WHERE t.title_id = s.title_id
AND s.ord_date = (SELECT MAX(sales.ord_date) FROM sales))
返回的必须是单个数据集才可以
SET ytd_sales =
(select t.ytd_sales + s.qty FROM titles t, sales s WHERE t.title_id = s.title_id
AND s.ord_date = (SELECT MAX(sales.ord_date) FROM sales));我没有测试。
UPDATE titles
SET ytd_sales = (select t.ytd_sales + s.qty from titles t, sales s WHERE t.title_id = s.title_id
AND s.ord_date = (SELECT MAX(sales.ord_date) FROM sales))
WHERE titles.title_id = (select title_id from sales where ord_date = (SELECT MAX(sales.ord_date) FROM sales))
UPDATE titles
SET ytd_sales = titles.ytd_sales +
(select qty
FROM sales s
WHERE titles.title_id = s.title_id
AND s.ord_date = (SELECT MAX(sales.ord_date) FROM sales)) 不可以吗?