Question

我不明白为什么我的查询无法正常工作，请帮助

select *
from 
(
    select Semester, StudentID, CourseCode, MarksObtained,CourseWeekName
from dstp_dm.lms.vStudentQuizResult
where CourseWeekName<='Week 04'

) aa
Full Outer join 
(
  select Semester,StudentID,CourseCode,Score,CourseWeekName
  from lms.vStudentAssignment
  where CourseWeekName<='Week 04'

)

Answer 1

可能是因为where CourseWeekName<='Week 04'。如我所见，CourseWeekName是字符串，而不是数字，因此您不能使用像<=

这样的比较运算符

Answer 2

第二个表中缺少别名

select aa.*,bb.*
from 
(
    select Semester, StudentID, CourseCode, MarksObtained,CourseWeekName
from dstp_dm.lms.vStudentQuizResult
where CourseWeekName<='Week 04'

) aa
Full Outer join 
(
  select Semester,StudentID,CourseCode,Score,CourseWeekName
  from lms.vStudentAssignment
  where CourseWeekName<='Week 04'

)bb on aa.StudentID=bb.StudentID

Answer 3

FULL OUTER JOIN仍然需要一个JOIN条件（on col1 = col2）什么不起作用？查询是引发错误还是给出错误的结果？如果查询运行但给出错误结果，则分别运行。

请帮助我了解错误是什么

3 个答案: