Question

我有两张桌子。一个持有员工，另一个持有项目。 Employee表具有主键，项目具有外键，用于标识哪个员工正在处理哪个项目。我需要编写一个查询，该查询将返回员工的名字和姓氏，但仅限于处理两个或更多项目的员工。这就是我到目前为止所做的：

create table employee
(
employeeId int not null identity(1,1) primary key,
firstName varChar(25) not null,
lastName varChar(25) not null,
gender varChar(1) not null,
dob date not null,
ssn varChar(9) not null,
)

insert into employee
 values 
    ('Peter','Smith','m','1979-08-25','123112233'),
    ('Juan','Doe','m','1985-05-22','435678907'),
    ('Rafael','Perez','m','1979-03-22','754984568'

create table projects
(
projectId int identity(1,1) primary key not null,
description varChar(100) not null,
status varChar(10) not null,
startDate date not null,
projectedEndDate date not null,
manager int foreign key references employee(employeeId)

）

insert into projects
values ('this project will improve the power on certain devices','active','2014-09-12','2015-0101','1'),
   ('this project will improve the user interface','active','2014-09-12','2015-01-01','1'),
   ('this project will improve the load time','active','2014-09-12','2015-01-01','2'),
   ('this project will implement stronger security','active','2014-09-12','2015-01-01','2')

   select firstname +' '+ lastname as fullname 
   from projects 
   inner join employee 
   on employee.employeeid = projects.manager

返回

Peter Smith
Peter Smith
Juan Doe
Juan Doe
Rafael Perez

我已经读过使用点数，但是还没有能够实现计数的加入，已经坚持了一段时间。

Answer 1

您需要group by和having子句：

select firstname +' '+ lastname as fullname 
from projects inner join
     employee 
     on employee.employeeid = projects.manager 
group by firstname +' '+ lastname
having count(*) >= 2;

Answer 2

你总是可以包装SQL：

SELECT fullname FROM (
   select firstname +' '+ lastname as fullname 
   from projects 
   inner join employee 
   on employee.employeeid = projects.manager ) t
GROUP BY fullname
HAVING COUNT(distinct projectId) > 1

我需要帮助在sql上创建一个查询

2 个答案: