您如何看待我在mysql工作台中的表？链接表？

您的数据库结构没有链接的可能性。

没有表具有可以将其链接到另一个表的键。

您必须识别一对多和多对多关联，并使用适当的键表示方法来表达它们。

例子：

我想表学生和表课程之间存在多对多的关系，您应该用这样的表来表达：

ideleve | idcourse

您必须在结构上计算出所有这些关系才能设计任何查询。

Following your comments I update the answer. In reality I should vot to close this question, as it is too broad and not over coding.

EXAMPLE OF PROBLEM SETTING:

Each student is identified by:
id | name | surname | born_date

Each course is identified by
id | course_title

Students can enroll in multiple courses

Courses can be held in 1st, 2nd semester or both maintaining the same id and title

There are up to 3 exams per course per semester

Notes of each exam can go from 1 to 5 with 1 being the lowest

Students have to take all the exams, if they do not take an exam their vote is considered 0 for that exam

This would led to a possible:

DB STRUCTURE

table students
id_student | name | surname

table courses
id_course | course_title

table exams
id_student | id_course | semester | exam | grade

with the implicit relations you can understand from columns names.

Then you can start with coding...

But here I am making a whole lot of assumptions on students, courses, exams and gardes and their relationships!

To design a DB an analysis of entities and relationships is needed.

the program you are trying to make is surely very simple as you say, also this analysis is not complex, but has to be done, and none can do that for you.

Following your last comment that finally clarify the problem you can do:

DB STRUCTURE

table students
id_student | name | surname | birthdate

table courses
id_course | course_title | year | semester

table exams
id_student | id_course | year | semester | test | exam | grade

example of table exams could be:

id_student | id_course | year | semester | test | exam | grade
--------------------------------------------------------------
  2701     |  K409     | 2015 |    1     |   1  | NULL |  4
  2701     |  K409     | 2015 |    1     |   2  | NULL |  4
  2701     |  K409     | 2015 |    1     |   3  | NULL |  4
  2701     |  K409     | 2015 |    0     | NULL | NULL |  3
  2701     |  K405     | 2015 |    1     |   1  | NULL |  4
  2701     |  K405     | 2015 |    1     |   2  | NULL |  4
  2701     |  K405     | 2015 |    1     |   3  | NULL |  4
  2705     |  K405     | 2015 |    0     | NULL | NULL |  3
  2705     |  K409     | 2015 |    2     |   1  | NULL |  4
  2705     |  K409     | 2015 |    2     |   2  | NULL |  4
  2705     |  K409     | 2015 |    2     |   3  | NULL |  4
  2705     |  K409     | 2015 |    0     | NULL | NULL |  3
  2705     |  K407     | 2015 |    2     |   1  | NULL |  4
  2705     |  K407     | 2015 |    2     |   2  | NULL |  4
  2705     |  K407     | 2015 |    2     |   3  | NULL |  4
  2705     |  K407     | 2015 |    0     | NULL | NULL |  3

You can link courses to exams/test using multi-columns key:

 id_course-year-semester

link student to exams/test with:

 id_student

通过您拥有的考试/测试表将学生链接到课程：

id_student | id_course-year-semester

这意味着当学生注册课程时，这样的记录将出现在考试/测试表中：

id_student | id_course | year | semester | test | exam | grade
--------------------------------------------------------------
  2701     |  K409     | 2015 |    1     | NULL | NULL |  NULL

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