SQL：查找平均分数

Question

鉴于该表，我正在寻找一个查询来计算给定教师的给定问题的平均分数。

如果我要在这个表格中添加另一个列，例如SCHOOLID，并希望有一个列来计算该学校给定问题的平均值，我该怎么做？

提前感谢您的所有帮助！

Answer 1

select teacherId, questionid, AVG(Score)
From myTable
group by teacherId, questionid

Answer 2

您可以创建存储过程来处理整个要求

CREATE PROCEDURE avarageCalc
(
   @teacherid nvarchar(5) = null,
   @questionid int = null,
   @schoolid int = null
)
AS
Begin

    SELECT AVG(SCORE) as Avarage 
                   FROM Table 
                   WHERE (TeacherID = @teacherid OR @teacherid IS NULL) AND 
                         (QuestionId = @questionid OR @questionid IS NULL) AND
                         (SchoolId = @schoolid OR @schoolid IS NULL)

END

Answer 3

你可以这样做：

SELECT TeacherId, QuestionId, AVG(Score)
FROM TABLE-NAME
GROUP BY TeacherId, QuestionId

以下是一些有用的链接：

1. 3schools
2. SQL Server - MSDN