mysql--从不订购的客户

                                                

解法一：（左外连接 + not null）

select A.Name as Customers
from Customers A left join Orders B
on A.Id = B.CustomerId
where B.Id is null

　　

解法二：（not in + 子查询）

select Name  as Customers  from Customers c where c.Id not in(
    select CustomerId from Orders 
)