sql-server - 使用 MSSQL 计算 id 的唯一出现次数

Question

我正在尝试计算每年唯一出现的教师。我确信结果不是唯一的。

我的查询

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

FROM tblTeachers INNER JOIN tblTeacher_Building 
.
.

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

结果（计算 TeacherID 的重复项）

我也试过

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

FROM tblTeachers INNER JOIN tblTeacher_Building 
.
.

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

我错过了什么？

谢谢

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

你很近。我想这就是你要找的：

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