DAY01-Selection

595. Big Country - LeetCode

select name,population,area 
from World 
where area >=3000000 or population >=25000000;

1757. Recyclable and Low Fat Products - LeetCode

select product_id 
from Products 
where (low_fats = 'Y') and (recyclable = 'Y');

584. Find User Referrals - LeetCode

select name
from customer 
where referee_id !=2 OR referee_id is NULL;

183. Customers who never order - LeetCode - Left Outer Join

SELECT c.Name as Customers 
from Customers c left join Orders o
on c.Id = o.CustomerId
where o.Id is NULL;

Joint table query:

internal link

select 字段 from 表1 inner join 表2 on 连接条件

outer join

(21 messages) MySql joint table query - Blog - CSDN Blog