Question

我试图写一个查询，建议学生注册哪些课程。查询将选择合适的课程，并将验证1）他们完成的课程。以及他们需要做什么2）要完成的前提课程.3）验证时间冲突。为了推荐他最好的课程。

我做了那些表并加入了它们，但是连接操作不起作用。什么语法是正确的？如果没有先决条件我将如何检查该怎么办？一些先决条件是高级还是初级是需要单独的表？

错误1064（42000）：您的SQL语法有错误;查看与您的手册相对应的手册在'studyplan sp on（t.std_id = sp.std_is）附近使用正确语法的MYSQL服务器版本 left outer join prerequsit p on（p.preid = c。'at line 3

     select c.*
    from std t
   inner join schedule22  c studyplan sp
   on (t.std_id=sp.std_id)
   left outer join prerequsit p
   on (p.preid=c.courseid)
   inner join schedule22 c
   on (c.courseid=p.courseid)
   where t.std=1 AND
   sp.complated='No' AND
   sp.passed='No' AND
   p.preid=courseid;

学生

enter code here

  std_id       username    pass   fname     email


   1             hjh                154     jdf         example@live.com



    Studyplan

  Courseid   code  `prerequisite        std_id    completed    passed
   2       UNS 100   No Prerequisite     1         Y             Y
     3,   'ENG 100',   'No Prerequisite',    1, 'Y', 'Y'),
     5,  'MTT 101',   'MTG 100',   1, 'Y', 'Y'),
     6, 'MTT 202',   'MTT 101', 1, 'Y', 'N'),
    (7, 'STT 100', 'No Prerequisite', 1, 'N', 'N'),
    (8, 'MTT 102','MTT 101', 1, 'N', 'N'),
    (9, 'ENG 200','english1', 1, 'N', 'N'),
    (10, 'OE1',3, 'NULL', 1, 'N', 'N'),
    (11, 'ENG 201','ENG 200', 1, 'N', 'N'),
    (12, 'CSC 302', 'MTT 202', 1, 'N', 'N'),
    (13, 'STT 201',, 'STT 100', 1, 'N', 'N'),
    (15, 'CSC 201','MTT 101 or MTT 102', 1, 'N', 'N'),
    (16, 'CSC 202', 'CSC 201', 1, 'N', 'N'),
    (17, 'PSY 201', 'ENG 100 + UNS 100', 1, 'N', 'N'),
    (18, 'NSC 201', 'No Prerequisite', 1, 'N', 'N'),
    (19, 'CSC 307', 'CSC 201', 1, 'N', 'N'),
   (20, 'CSC 301','CSC 202', 1, 'N', 'N'),
   (21, 'ITE 390', 'Junior Level', 1, 'N', 'N'),
   (22, 'CSC 305', 'Junior Level', 1, 'Y', 'Y'),
   (23, 'ITE 305', ' 'Junior Level', 1, 'Y', 'Y'),
   (24, 'ITE 414', ', 'junior Level', 1, 'Y', 'Y'),
   (25, 'CSC 308',  'CSC 301', 1, 'N', 'N'),
   (26, 'ITE 402', 'CSC 305', 1, 'N', 'N'),
  (27, 'CSC 311', 'CSC 201', 1, 'N', 'N'),
  (28, 'ITE 422',  'CSC 305', 1, 'N', 'N'),
 (29, 'CIS 401',  'CSC 302', 1, 'N', 'N'),
 (30, 'ITE 409',  'Senior Level', 1, 'N', 'N'),
 (31, 'CIS 401',  'CSC 302', 1, 'N', 'N'),
 (32, 'CSC 401', 'ITE 305', 1, 'N', 'N'),
 (33, 'ITE 409', 'Null', 1, 'N', 'N'),
  (34, 'ITE 408',  'CSC 305', 1, 'N', 'N')

附表

enter code here

 semester`, `courseid`, `coursecode`, `section`,`date`, `time`, `,`sch_id`) 
  ('fall', 9, 'ENG 100', 51,'MoWe', '1:45PM-3:15PM', 'staff',1),
  ('fall', 16, 'CSC202', 51, 'Mo-We',' 1:45PM-3:15PM', 'staff',1),
  ('fall', 26, 'ITE402', 51, 'Tu','10:30-12pm', 'staff',1),
  ('fall', 6, 'MTT 202', 51,'Su-Tu', '12:00-2:00PM', 'staff',1),
  ('fall', 8, 'MTT 102', 51','SuTu',' 12:00-2:00PM', 'staff',1),
  ('fall', 12, 'CSC 302', 51,'Mo-We',' 10:00-12:00PM', 'staff',1),
  ('fall', 15, 'CSC 201', 52,'Mo-We',' 10:00-12:00PM', 'staff',1),
  ('fall', 21, 'ITE 390', 51, 'Su-Tu',' 12:00-2:00PM', 'staff',1),
  ('fall', 5, 'MTT 101', 51, 'Su',' 4:00PM -7:00PM', 'staff',1),


   ('fall', 28, 'ITE 422', 51, Su-Tu',' 12:00-2:00PM', 'staff',1);

prerequsit`

enter code here

    (`courseid`, `preid`) VALUES
       (5, 1,),
       (6, 2),
       (8, 3),
      (9, 4),
       (11, 5),
      (12, 6),
      (13, 7),
      (14, 8),
     (15, 9),
      (16, 10),
     (17, 11),
    (18, 12),
     (19, 13),
    (20, 14),
    (21, 21),
    (22, 22),
   (23, 23),
    (24, 24),
   (25, 20),
 (26, 22),
  (27, 25),
  (28, 22),
  (29, 12),
  (30, 30),
 (32, 23),
  (34, 22,),
  (35, 12),
  (36, 22),
  (37, 3),

Answer 1

您的查询在from子句中包含schedule22 c两次。那是一个错误。可能会有更多。

SQL查询：如何验证已完成课程的先决条件以及如何查找课程时间冲突？

1 个答案: