选择Max with group by

Question

  

我有下表。

我需要选择SemesterID，AcadamiYear，2015年最高学年和学术学期的学术学期

预期输出

  

2013 1 2

我尝试了以下查询，但它返回了两个记录

select MAX(AcadamiYear) as Year,
  MAX(AcadamicSemester) as Semester
  ,SemesterID
  from
  tblSemesterRegistration 
  where [IntakeYear]='2015'
  Group by SemesterID

Answer 1

由于您正在搜索单个记录，因此您可以使用TOP 1，按您的意图排序

select TOP 1 *
  from
  tblSemesterRegistration 
  where [IntakeYear]='2015'
  Order by AcadamiYear DESC, AcadamicSemester DESC

Answer 2

这是您正在寻找的查询：

SELECT SR.*
FROM tblSemesterRegistration SR
INNER JOIN (SELECT MAX(SR2.AcadamiYear) AS [AcadamiYear]
                  ,MAX(SR2.AcadamicSemester) AS [AcadamicSemester]
                  ,IntakeYear
            FROM tblSemesterRegistration SR2
            GROUP BY SR2.IntageYear) T ON T.AcadamiYear = SR.AcadamiYear
                                         AND T.AcadamicSemester = SR.AcadamicSemester
                                         AND T.IntakeYear = SR.IntakeYear
WHERE SR.IntakeYear = '2015'

希望这会对你有所帮助。

Answer 3

SELECT MAX(AcadamiYear) AS Year,
    MAX(AcademicSemester) AS Semester,
    MAX(SemesterID) AS SemesterID
FROM tblSemesterRegistration 
WHERE [IntakeYear] = '2015'
GROUP BY IntakeYear

Answer 4

如果SemesterID是主键，则对其进行分组将始终产生所有行（因为它始终是唯一的）。

我猜你的意思是找回参数设置的那个学期id：

select r.*
from   tblSemesterRegistration r
join   ( select max(AcadamiYear) as Year
         ,      max(AcadamicSemester) as Semester
         from   tblSemesterRegistration 
         where  [IntakeYear]='2015'
       ) m
on     r.acadamiyear = m.year
and    r.acadamicsemester = m.semester