这 是一个电商项目，做的是报表的展示，我还以为要请求几次，结果，用一个SQL全部查完了
下面是目标效果图
这是我的SQL
代码
SELECT
product.NAME,
product.price,
pros.order_num,
product.price * pros.count_product sum_price,
ads.create_time,
ads.contact_address,
ads.contact_name,
ads.contact_mobile
FROM
product,
(
SELECT
order_num,
product_id,
COUNT(product_id) count_product
FROM
order_item
WHERE
order_num = "O2020100500001"
GROUP BY
product_id
) pros,
(
SELECT
of.create_time,
ot.product_id pid,
of.contact_address,
of.contact_name,
of.contact_mobile
FROM
order_item ot,
order_info of
WHERE
of.order_num = "O2020100500001"
AND ot.order_num = "O2020100500001"
) ads
WHERE
id IN (
SELECT
product_id
FROM
order_item
WHERE
order_num = "O2020100500001"
GROUP BY
product_id
)
AND id = pros.product_id and id = ads.pid
group by id
这是我的查询效果
总结
在sql之中，可以使用结果集做为表来查询（以前会，只不过忘了）
在sql之中，可以使用这个嵌套查询来做为复杂查询（会牺牲效率，但鬼换取的是一劳永逸）
