Question

我有2个表：“members_info”和“members_lesson”。

假设在members_info中我有字段member_id，first_name，last_name 在members_lesson中，我有members_lesson_id，lesson_id，member_id

我想创建一个查询，在那里我可以看到已经完成一个课程但没有完成另一个课程的成员。我试过这个问题：

SELECT members_info.member_id
   FROM members_info
   JOIN member_lessons ON members_info.member_id = member_lessons.member_id
   WHERE member_lessons.lesson_id =6 AND  member_lessons.lesson_id !=7

但该查询无效。当我只检查该成员是否已完成课程时，它可以工作，但如果我想查看该成员是否还没有完成另一个成员，它就不起作用。有任何想法吗？谢谢！

编辑 -

我试过了：

SELECT members_info
FROM members_info
WHERE member_id IN (SELECT member_id FROM member_lessons WHERE lesson_id = 6)
AND member_id NOT IN (SELECT member_id FROM member_lessons WHERE lesson_id = 7)

它确实有效，但我不确定性能。这样好吗？谢谢！

Answer 1

试试这个：

SELECT member_id, max(lesson_id)   
FROM member_lessons ml 
group by member_id 
WHERE lesson_id in (6, 7)
having count(distinct lesson_id) = 1
    and max(lesson_id) = 6

Answer 2

SELECT members_info FROM members_info WHERE member_id IN（SELECT member_id FROM member_lessons WHERE lesson_id = 6） AND member_id NOT IN（SELECT member_id FROM member_lessons WHERE lesson_id = 7）

Mysql查询，看一个成员是否已经完成了一课

2 个答案: