使用MSSQL計算唯一出現的IDid

Question

我想要計算每年teacherids的唯一出現次數。我相信結果不是唯一的。

我查詢

SELECT DISTINCT count (tblTeachers.TeacherID) AS uniqueTeacherCount, tblSchoolYears.SchoolYear 

FROM tblTeachers INNER JOIN tblTeacher_Building 
. 
. 

GROUP BY tblSchoolYears.SchoolYear 
ORDER BY tblSchoolYears.SchoolYear DESC; 

我也曾嘗試

SELECT COUNT(DISTINCT tblTeachers.TeacherID) AS uniqueTeacherCount, tblSchoolYears.SchoolYear 

FROM tblTeachers INNER JOIN tblTeacher_Building 
. 
. 

GROUP BY tblSchoolYears.SchoolYear 
ORDER BY tblSchoolYears.SchoolYear DESC; 

我缺少什麼結果（即指望TeacherID的副本）？

謝謝

Answer 1

Select Count(TeacherID) AS uniqueTeacherCount,SchoolYear 
from 
(
SELECT DISTINCT tblTeachers.TeacherID, tblSchoolYears.SchoolYear 
FROM tblTeachers INNER JOIN tblTeacher_Building 
. 
. 
) hlp 
GROUP BY SchoolYear 
ORDER BY SchoolYear DESC; 

Answer 2

你靠近。我認爲這是你要找的東西：

SELECT COUNT(*) 
FROM 
(
SELECT DISTINCT count (tblTeachers.TeacherID) AS uniqueTeacherCount, tblSchoolYears.SchoolYear ... 
)