mysql语法错误查询

Question

以下是我的数据库的快照：http://postimg.org/image/p3hj9pw3n/

我对这个mysql查询语法有这个问题：

 SELECT a.examid        AS ei,
       a.examname      AS en,
       f.subtitle      AS st,
       b.day           AS d,
       b.timestart     AS ts,
       b.timeend       AS te,
       c.attemps       AS a,
       d.employeelname AS ln,
       d.employeefname AS fn,
       d.employeemname AS mn
FROM   exams a,
       examsched b,
       scores c,
       employees d,
       students e,
       subjectlist f
WHERE  a.examid = b.exams_examid
       AND a.examid = c.exams_examid
       AND a.employees_empid = d.empid
       AND c.students_studnum = e.studnum
       AND a.subjectlist_subcode = f.subcode
ORDER  BY b.day 

显示此类错误：

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'a.examid = b.exams_examid AND a.examid = c.exams_examid AND a.employees_empid = ' at line 1

我希望有人可以帮助我，提前谢谢！