每日sql -查询至少有5名下属的经理
背景需求
查询至少有5名下属的经理
DDL
Create table If Not Exists Employee (Id int, Name varchar(255), Department varchar(255), ManagerId int);insert into Employee (Id, Name, Department, ManagerId) values (101, 'John', 'A', null);insert into Employee (Id, Name, Department, ManagerId) values (102, 'Dan', 'A', 101);insert into Employee (Id, Name, Department, ManagerId) values (103, 'James', 'A', 101);insert into Employee (Id, Name, Department, ManagerId) values (104, 'Amy', 'A', 101);insert into Employee (Id, Name, Department, ManagerId) values (105, 'Anne', 'A', 101);insert into Employee (Id, Name, Department, ManagerId) values (106, 'Ron', 'B', 101);
SQL 解决代码
select Name from Employee t1 join (select ManagerId from Employee group by ManagerId having count(1) >=5) t2 on t1.Id = t2.ManagerId ;
#选举
背景
有一张表是选举表，一张表是投票表，选出票数最高的人，
DDL
Create table If Not Exists Candidate (id int, Name varchar(255));Create table If Not Exists Vote (id int, CandidateId int);insert into Candidate (id, Name) values (1, 'A');insert into Candidate (id, Name) values (2, 'B');insert into Candidate (id, Name) values (3, 'C');insert into Candidate (id, Name) values (4, 'D');insert into Candidate (id, Name) values (5, 'E');insert into Vote (id, CandidateId) values (1, 2);insert into Vote (id, CandidateId) values (2, 44);insert into Vote (id, CandidateId) values (3, 3);insert into Vote (id, CandidateId) values (4, 2);insert into Vote (id, CandidateId) values (5, 5);
解决方案
SELECT name AS 'Name'
FROM Candidate
JOIN (SELECT Candidateid FROM Vote GROUP BY Candidateid ORDER BY COUNT(*) DESC LIMIT 1 ) AS winner
WHERE Candidate.id = winner.Candidateid;