Sql ms access中的语法错误（缺少运算符）

我试图使用下面的查询，但是它表示缺少运算符和语法错误。此问题与ms access有关

select s.student_id, e.average_second_year_marks, e.average_third_year_marks, e.overall_marks
from students s
join
(
  select student_id,
    avg(case when program_year_when_enrolled = 'Second' then marks_obtained end)
      as average_second_year_marks,
    avg(case when program_year_when_enrolled = 'Third' then marks_obtained end)
      as average_third_year_marks,
    (
     (sum(case when program_year_when_enrolled = 'Second' then marks_obtained end) * 1.0) +
     (sum(case when program_year_when_enrolled = 'Third' then marks_obtained end) * 2.0)
    ) / 3.0 as overall_marks
  from enrollment
  group by student_id
) e on e.student_id = s.student_id
where s.course_current_status = 'Graduated-2017'

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等效的MS Access查询更像这样：

select s.student_id, e.average_second_year_marks,
       e.average_third_year_marks, e.overall_marks
from students as s inner join
     (select student_id,
             avg(iif(program_year_when_enrolled = "Second", marks_obtained, NULL)) as average_second_year_marks,
             avg(iif(program_year_when_enrolled = "Third", marks_obtained, NULL)) as average_third_year_marks
             (1.0 * avg(iif(program_year_when_enrolled = "Second", marks_obtained, NULL)) +
              2.0 * avg(iif(program_year_when_enrolled = "Third", marks_obtained, NULL)) 
             ) / 3.0 as overall_marks
     from enrollment
     group by student_id
    ) as e 
    on e.student_id = s.student_id
where s.course_current_status = "Graduated-2017";

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如果这是关于Microsoft Access的，那么为什么要标记MySQL和Postgres呢？我取下了标签。请仅添加相关的标记。MS Access不支持“CASE”语句，您需要将它们转换为

iif

语句。它在join子句中表示语法错误，但当我使用另一个join（如左join或外join）时，它会在join操作中表示语法错误。你能帮我做些什么吗。