183. Customers Who Never Order(SQL)

# Easy

# Write your MySQL query statement below
# is NULL的语法
select Name Customers from Customers
left join Orders on Customers.Id = Orders.CustomerId
where Orders.CustomerId is NULL;

# not in 语法
select Name Customers from Customers
where Id not in (select CustomerId from Orders);

不好做

is NULL 和 not in 语法很懵圈。