# $1821. 寻找今年具有正收入的客户
# https://leetcode.cn/problems/find-customers-with-positive-revenue-this-year/

# SQL架构
Create table If Not Exists Customers (customer_id int, year int, revenue int);
Truncate table Customers;
insert into Customers (customer_id, year, revenue) values ('1', '2018', '50');
insert into Customers (customer_id, year, revenue) values ('1', '2021', '30');
insert into Customers (customer_id, year, revenue) values ('1', '2020', '70');
insert into Customers (customer_id, year, revenue) values ('2', '2021', '-50');
insert into Customers (customer_id, year, revenue) values ('3', '2018', '10');
insert into Customers (customer_id, year, revenue) values ('3', '2016', '50');
insert into Customers (customer_id, year, revenue) values ('4', '2021', '20');

# Write your MySQL query statement below
select
    customer_id
from
    Customers
where
    year = 2021
    and revenue > 0;

# clean-up
drop table Customers;