mysql - 需要获取所有当月未付款的学生

Question

我有两张 table

学生表:

id   studentname   admissionno
3    test3               3
2    test2               2
1    test                1

第二张表是费用:

id   studentid  created
1       3       2015-06-06 22:55:34
2       2       2015-05-07 13:32:48
3       1       2015-06-07 17:47:46

我需要获取当月未付款的学生，
我正在执行以下查询:

SELECT studentname FROM students 
    WHERE studentname != (select students.studentname from students
    JOIN submit_fee
    ON (students.id=submit_fee.studentid)
    WHERE MONTH(CURDATE()) = MONTH(submit_fee.created)) ;

我收到错误:

'#1242 - Subquery returns more than 1 row'

你能告诉我获取当月未付款的所有学生的正确查询是什么吗？

Answer 1

使用不在，请尝试以下查询:

SELECT s.*
FROM students s
WHERE s.id NOT IN ( SELECT sf.studentid FROM studentfees sf WHERE month(sf.created) = EXTRACT(month FROM (NOW())) )