没有子查询和连接的SQL查询

3 回答

• 1

  只需一门课程即可为学生检索STUDENT_ID：

  SQL>  SELECT student_id
    2   FROM students 
    3   GROUP BY student_id
    4   HAVING COUNT(course_id) = 1 
    5   /
  
  
  STUDENT_ID
  ----------
           4
           3
  
  Elapsed: 00:00:00.09
  SQL>
  

  但是为了获得其他信息，例如课程名称，我们需要使用子查询或连接 .

  回复于 2024-04-30T02:16:17+08:00
• -2

  使用 group by 与 having

  select student_id,count(course_id) as num 
  from students group by student_id
  having num =1
  

  或这个 ：-

  select student_id
  from students group by student_id
  having count(course_id) =1
  

  回复于 2024-04-30T02:16:17+08:00
• 1

  如何使用 GROUP BY 和 HAVING COUNT

  SELECT student_id, course_name FROM students 
  GROUP BY student_id, course_name
  HAVING COUNT(course_id) = 1
  

  回复于 2024-04-30T02:16:17+08:00