Question

我有以下表格

student(student_id, name)
assignment(student_id, course_code, assignment number)

我正在尝试编写一个查询来返回那些已为特定课程提交了作业编号1而不是作业编号2的学生

我已经编写了以下查询，但很难在每个课程的基础上返回结果。有什么建议吗？

SELECT name, a.student_id, course_code
FROM assignment a INNER JOIN student s
on a.student_id = s.student_id
WHERE assignment_number = 1
AND assignment_number != 2

Answer 1

SELECT name, a.student_id, course_code
FROM assignment a INNER JOIN student s
on a.student_id = s.student_id
WHERE assignment_number = 1
AND not exists (select * from
                assignment a2 inner join student s2 
                where a2.student_id = s2.student_id
                and s2.student_id = s.student_id
                and a2.assignment_number = 2)

这是在行动中看到它的小提琴： http://sqlfiddle.com/#!2/48997/2

Answer 2

SELECT 
  s.name, 
  s.student_id, 
  a.course_code
FROM 
  assignment a 
INNER JOIN 
  student s
ON 
  a.student_id = s.student_id
WHERE 
  assignment_number in( 1,2 ) 
GROUP BY 
  s.name, 
  s.student_id, 
  a.course_code
HAVING max(assignment_number) = 1

Answer 3

已完成作业1的学生名单，但未已完成作业2：

select s.name, a.student_id, a.course_code
from assignment a
inner join student  s on a.student_id = s.student_id
where a.student_id in 
    (Select student_id from assignment
    where assignment_id = 1) -- All students that submitted Assignment 1
and a.assignment_id !=2

在where子句中编写子查询

3 个答案: