1到多个选择和连续

Question

我有两张桌子：

[customer]
id
name

[customer_photo]
id
customer_id
photo

我想选择所有客户及其照片。

此查询正在执行此操作，但只获取至少拥有一张照片的用户：

SELECT customer.id, name, GROUP_CONCAT(cp.photo) as photos 
FROM customer 
JOIN customer_photo cp ON cp.customer_id = customer.id 
GROUP BY customer.id

我希望得到所有用户，即使他们没有照片。

Answer 1

只需添加LEFT加入

即可

SELECT customer.id, name, GROUP_CONCAT(cp.photo) as photos 
FROM customer 
LEFT JOIN customer_photo cp ON cp.customer_id = customer.id 
GROUP BY customer.id