在where子句中编写子查询

Question

我有下表

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

我正在尝试编写查询以返回已提交特定课程的作业编号1但未提交作业编号2的那些学生

我已经编写了以下查询，但是在查询过程中却很挣扎。 有什么建议么？

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)

这是查看实际操作的小提琴： 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但尚未完成作业2的学生列表：

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