管理器表:
create table Manager(id integer, name varchar(100));
insert into Manager(id, name) values(1, "M1");
insert into Manager(id, name) values(2, "M2");
insert into Manager(id, name) values(3, "M3");
employee表以及manager id(m\ U id)
create table Employee(id integer, m_id integer, name varchar(100));
insert into Employee(id, m_id, name) values(11, 1,"E1");
insert into Employee(id, m_id, name) values(12, 1,"E2");
insert into Employee(id, m_id, name) values(13, 2,"E3");
执行的查询:
select M.id, M.name, count(E.id) from Manager as M, Employee as E where E.m_id=M.id group by E.m_id, M.id, M.name;
输出:
1 M1 2
2 M2 1
预期产量:
1 M1 2
2 M2 1
3 M3 0
请帮助我如何包括m3经理以及分配给他的0名员工?
1条答案
按热度按时间shyt4zoc1#
你应该用左连接