Question

我有这个查询，并且为了查询经理部门名称总是在标题中得到错误：

select e.employee_id e_id 
      , e.first_name || '  ' || e.last_name employee_name  
      , e.job_id 
      , e.department_id 
      , e.department_name 
      , e.salary || ' $ '
      , to_char(e.hire_date , ' day- dd - mon -yyyy' ) employee_hire_date
      , m.employee_id  m_id
      , m.first_name || '  ' || m.last_name manager_name  
      , m.job_id 
      , m.department_id  
      , m.department_name 
      , m.salary 
FROM employees e 
JOIN employees m 
  on m.employee_id = e.manager_id 
JOIN departments d
  on d.department_id = e.department_id 
JOIN departments d
  on d.department_id = m.department_id

Answer 1

问题出现在这里：

JOIN departments d
  on d.department_id = e.department_id 
JOIN departments d
  on d.department_id = m.department_id

要么删除它们中的一个，因为您没有从这些表中选择任何内容，employee表中的所有内容都存在，或者它们的别名不同。

JOIN departments d
  on d.department_id = e.department_id 
JOIN departments dd
  on dd.department_id = m.department_id

当您尝试使用具有相同名称/别名的两个不同列时，将发生此错误。每列必须有自己唯一的名称/别名。

Answer 2

您使用了两次相同的别名。请尝试以下方法：

select e.employee_id e_id 
      , e.first_name || '  ' || e.last_name employee_name  
      , e.job_id 
      , e.department_id 
      , e.department_name 
      , e.salary || ' $ '
      , to_char(e.hire_date , ' day- dd - mon -yyyy' ) employee_hire_date
      , m.employee_id  m_id
      , m.first_name || '  ' || m.last_name manager_name  
      , m.job_id 
      , m.department_id  
      , m.department_name 
      , m.salary 
FROM employees e join employees m 
  on m.employee_id = e.manager_id 
JOIN departments d
  on d.department_id = e.department_id 
JOIN departments d2
  on d2.department_id = m.department_id

Answer 3

不同地区分部门名称并更正选择假设department_Id和部门名称来自部门。

select e.employee_id e_id 
      , e.first_name || '  ' || e.last_name employee_name  
      , e.job_id 
      , de.department_id            --***This line Updated alias
      , de.department_name          --***this line  Updated alias
      , e.salary || ' $ '
      , to_char(e.hire_date , ' day- dd - mon -yyyy' ) employee_hire_date
      , m.employee_id  m_id
      , m.first_name || '  ' || m.last_name manager_name  
      , m.job_id 
      , dm.department_id            --***This line Updated alias
      , dm.department_name          --***This line Updated alias
      , m.salary 
FROM employees e 
JOIN employees m 
  on m.employee_id = e.manager_id 
JOIN departments de                      --***this line Updated alias
  on de.department_id = e.department_id  --***this line Updated alias
JOIN departments dm                      --***this line Updated alias
  on dM.department_id = m.department_id  --***this line Updated alias

第1行的错误：ORA-00918：列模糊定义

3 个答案: