错误：ORA-00937

Question

我想创建一个表 NEW_DEPTS。我有 DEPARTMENT_ID 和 DEPARTMENT_NAME，它们位于 DEPARTMENTS 表中。

            desc departments
            Name                            Null?    Type
            ------------------------------- -------- ----
            DEPARTMENT_ID                   NOT NULL NUMBER(4)
            DEPARTMENT_NAME                 NOT NULL VARCHAR2(30)
            MANAGER_ID                               NUMBER(6)
            LOCATION_ID                              NUMBER(4)

我的 EMPLOYEES 表包含：

            desc employees
            Name                            Null?    Type
            ------------------------------- -------- ----
            EMPLOYEE_ID                     NOT NULL NUMBER(6)
            FIRST_NAME                               VARCHAR2(20)
            LAST_NAME                       NOT NULL VARCHAR2(25)
            EMAIL                           NOT NULL VARCHAR2(25)
            PHONE_NUMBER                             VARCHAR2(20)
            HIRE_DATE                       NOT NULL DATE
            JOB_ID                          NOT NULL VARCHAR2(10)
            SALARY                                   NUMBER(8,2)
            COMMISSION_PCT                           NUMBER(2,2)
            MANAGER_ID                               NUMBER(6)
            DEPARTMENT_ID                            NUMBER(4)

现在，我想创建一个 NEW_DEPTS 表，其中应包含 DEPARTMENT_ID 和 DEPARTMENT_NAME 以及每个部门的总 SALARY。每个部门都有一定数量的员工，因此，对于部门编号 10、20、30 等，应计算总工资。

我的主要查询是：

           create table new_depts as
           select d.department_id,d.department_name,sum(e.salary) dept_sal
           from employees e,departments d
           where e.department_id = d.department_id;

我遇到了一个错误：

           select d.department_id,d.department_name,sum(e.salary) dept_sal
              *
           ERROR at line 2:
           ORA-00937: not a single-group group function

所以，我用谷歌搜索了它。我发现像 sum、avg、max、min 这样的组函数不能在 select 语句中使用。我需要 GROUP BY 子句。所以，我想单独解决它。因此，我跳过了“create table...”语句并写道：

           select distinct d.department_id,d.department_name,sum(e.salary) dept_sal
           from employees e,departments d
           where e.department_id = d.department_id
           group by department_id;         

我得到错误：

           group by department_id;
                  *
           ERROR at line 4:
           ORA-00911: invalid character      

然后我写道：

           select d.department_id,d.department_name,sum(e.salary) dept_sal
           from employees e,departments d
           where e.department_id = d.department_id
           group by d.department_id;

我收到错误：

           select d.department_id,d.department_name,sum(e.salary) dept_sal
                   *
           ERROR at line 1:
           ORA-00979: not a GROUP BY expression

然后我写道：

           select d.department_id,d.department_name,sum(e.salary) dept_sal
           from employees e,departments d
           where e.department_id = d.department_id
           group by department_id;

我收到错误：

           group by department_id
                   *
           ERROR at line 4:
           ORA-00918: column ambiguously defined

我知道它是一个“加入”。但不知道我应该如何放置 GROUP BY 子句，以便我的 GROUP FUNCTION 可以正确运行。

Answer 1

您需要按不在聚合函数中的所有列进行分组，并且由于您已定义表别名，因此您必须在列中使用该别名。错误ORA-00918: column ambiguously defined 是因为您有两个名为department_id 的列，因此您必须指定department_id 来自的表：

select d.department_id,
  d.department_name,
  sum(e.salary) dept_sal
from employees e
inner join departments d
  on e.department_id = d.department_id
group by d.department_id, d.department_name;

您会注意到我将查询更改为使用 ANSI JOIN 语法 (INNER JOIN)。