Sql server 用于检索结果而不重复的SQL查询

我有一个名为Schedule的表，其中包含名为TeacherName和ClassTakenDate的字段。表中的值如下所示：

TeacherName       ClassTakenDate

Anish              2011-10-01

Anish              2011-10-01

John               2011-10-01

John               2011-10-02

我想要这样的结果：

TeacherName               NoOfDays

Anish                        1

John                         2

---

我们如何做到这一点？

ClassTakenDate

不应该在

SELECT

列表中，您需要

GROUP BY foo.TeacherName

SELECT TeacherName, 
       COUNT(DISTINCT ClassTakenDate) AS NoOfDays
FROM Schedule 
GROUP BY TeacherName

SELECT TeacherName, ClassTakenDate, COUNT( * ) AS NoOfDays 
FROM (
    SELECT DISTINCT TeacherName, ClassTakenDate
      FROM Schedule 
) AS foo
GROUP BY foo.ClassTakenDate