Question

我有两个包含以下信息的表

models

id      manufactor 
1       Mercedes
2       Ford
3       Volvo

orders
car_id customer_id
1      4
1      22
2      54
1      95

我想要一个查询，它将在一行中提供制造商名称以及每种模型的销售数量。

以下是我的尝试：

SELECT
  m.make
FROM models m
LEFT JOIN(
    SELECT COUNT(*)FROM orders
) o on o.car_id = m.id

Answer 1

试试这个：

SELECT m.manufactor, COUNT(o.car_id)
FROM models m
LEFT JOIN orders o ON m.id = o.car_id
GROUP BY o.car_id

Answer 2

SELECT m.make, sum(o.car_id) as total_sold FROM models as m 
LEFT JOIN SELECT  * from orders as o on o.car_id=m.id group 
by o.car_id order by o.car_id

Answer 3

您可以按如下方式更改查询

SELECT
m.make,o.totcount
FROM models m
LEFT JOIN(
SELECT COUNT(*) as totcount FROM orders group by car_id
) o on m.id = o.car_id

从两个表中获取信息

3 个答案: