编写SQL查询以查找已注册某个位置提供的单元的学生? [英] Write the SQL query to find students who are enrolled for units offered in a location?

问题描述

问题表我认为这三个表都将被使用.但是我无法建立一个表Student_1和Course之间的关系.

Problem Table " I think for this all three tables will be used. But I can't establish a relation between table Student_1 and Course.

@ APC该代码有效，但是只给2个学生而不是3个学生，我的桌子上有什么错误吗? 课程表 学生_2表 学生_1 来自@APC代码的答案

@ APCThis code is working.But giving only 2 students instead of 3, is there any mistake in my table?. Course table student_2 table Student_1 Answer from @APC code

推荐答案

对于学生ID，未选择任何行"

"for student id one no row selected "

计算机非常精确.他们将完全按照您编写的代码运行代码.您的查询具有以下WHERE子句:

Computers are extremely precise. They will run the code exactly as you write it. Your query has this WHERE clause:

location like '%burwood%'

但是，如果仔细查看course中的数据，您会发现location中的值是Burwood. 'Burwood'不等于'burwood'，因为前导字母的情况有所不同.

But if you look carefully at the data in course you will spot that the value in location is Burwood. 'Burwood' does not equal 'burwood' because of that difference in the case of the leading letter.

如果您这样编写WHERE子句，您将获得结果:

You would have gotten results if you had written your WHERE clause like this:

location like '%urwood%'

但是，最好使用相等过滤器进行过滤:

However it is always better to filter with an equality filter:

 select s1.student_id
        , s1.student_fname
        , s1.student_fname
        , c.course
 from course c
      join student2 s2 on s2.course_id = c.course_id
      join student1 s1 on s1.student_id = s2.student_id
 where c.location = 'Burwood';

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