使用Oracle的SQL中缺少表达式问题

Question

我想按部门获取员工人数，我使用Oracle编写了此脚本，但是它总是说缺少一个表达式

我的表中使用的列：

department :name (the name of the department) - 
depnum (the id of the department"primary key"), 
employee : empnum (the id of the employee) - 
depnum (the id of the department in which the employee in question is working "foreign key")

查询：

select 
    s.name 
from
    department s 
inner join 
    employee p on s.depnum = p.depnum 
group by 
    s.name 
having 
    count(p.empnum) = max(select count(p.empnum) 
                          from employee p, department s 
                          where s.depnum = p.depnum 
                          group by s.name) ;

Answer 1

如果您想要按部门划分的员工人数，则可能会发生以下情况：

select s.name, count(*) as num_employees
from department s inner join
     employe p
     on s.depnum = p.depnum 
group by s.name ;

如果您希望部门名称使用最多的名称，则可以使用having子句：

select s.name, count(*) as num_employees
from department s inner join
     employe p
     on s.depnum = p.depnum 
group by s.name 
having count(*) = (select max(cnt)
                   from (select count(*) as cnt
                         from employee e2
                         group by e2.depnum
                        ) e2
                  );

查询的问题是您尝试采用子查询的max() 。 该语法是不允许的-也是不必要的。

Answer 2

您的sql语句不正确，这就是它引发该错误的原因。 我认为您尝试了以下类似的操作

select s.name 
from department s 
inner join employe p on s.depnum=p.depnum 
group by s.name 
having count(p.empnum)=
select max(cnt) from 
( 
select count(p.empnum) as cnt
from employe p join department s 
on s.depnum=p.depnum 
group by s.name
 ) t;