MySQL刷题(Leecode)

简单部分

1.编写一个 SQL 查询，获取 Employee 表中第二高的薪水（Salary）

 select (select distinct Salary from Employee order by Salary desc limit 1 offset 1) as SecondHighestSalary;

2.给定一个 Weather 表，编写一个 SQL 查询，来查找与之前（昨天的）日期相比温度更高的所有日期的 Id

select A.Id from Weather A 
inner join Weather B 
on A.Temperature > B.Temperature
and datediff(A.RecordDate,B.RecordDate)=1

SELECT w1.Id FROM Weather w1, Weather w2  
WHERE w1.Temperature > w2.Temperature AND TO_DAYS(w1.RecordDate)=TO_DAYS(w2.RecordDate) + 1; 

3.您需要编写一个 SQL查询，找出所有影片描述为非 boring (不无聊) 的并且 id 为奇数 的影片，结果请按等级 rating 排列

select * from cinema 
where description not like'boring'
and id&1
order by rating

1. 给定 Employee 表，编写一个 SQL 查询，该查询可以获取收入超过他们经理的员工的姓名。

select A.Name from Employee A
inner join Employee B 
on A.ManagerId=B.Id
where A.Salary>B.Salary

5.编写一个 SQL 查询，查找 Person 表中所有重复的电子邮箱。

select distinct A.Email from Person A, Person B
where A.Email=B.Email and A.Id <> B.Id

select Email from Person group by Email having count(Email)>1

6.某网站包含两个表，Customers 表和 Orders 表。编写一个 SQL 查询，找出所有从不订购任何东西的客户。

select Name as Customers  
from Customers  
where Id not in(  
select C.Id  
from Customers as C, Orders as O  
where C.Id = O.CustomerId)  

7.编写一个 SQL 查询，满足条件：无论 person 是否有地址信息，都需要基于上述两表提供 person 的以下信息：

select Person.FirstName,Person. LastName, Address.City, Address.State from Person 
left join Address
on Person.PersonId=Address.PersonId

8.有一个courses 表 ，有: student (学生) 和 class (课程)。 请列出所有超过或等于5名学生的课

select class from courses 
group by class
having count(distinct student) >= 5

9.如果一个国家的面积超过300万平方公里，或者人口超过2500万，那么这个国家就是大国家。

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