Question

我试图将aggregate function与其他数学函数结合起来，例如：

SELECT student.name, (exam.midterm1 + +exam.midterm2 + SUM(student.grade*class.extracredit) AS FINALSCORE
FROM student, class, exam
WHERE student.name = class.studentname
GROUP BY student.name;

^它不会起作用。将聚合函数与sql中的其他数学函数组合的正确方法是什么？

学生表

NAME                           GRADE
------------------------- ----------
Jason                             44
Edward                            11
David                             95
Sean                              76
Jason                             88
David                             76

班级表

STUDENTNAME              EXTRACREDIT
------------------------- ----------
Jason                              4
Edward                             2
David                              1
Sean                               4

考试表

STUDENTNAME                 MIDTERM1        MIDTERM2
------------------------- ----------      ----------
Jason                             76             87
Edward                            60             80
David                             97             75
Sean                              82             79

Answer 1

仅计算学生表中多个等级的总和，并添加JOIN子句以加入学生，班级和考试表，然后使用简单的表达式对四个数值求和，例如：

SELECT 
    s.name, 
    s.total_grade + class.extracredit + 
       exam.midterm1 + exam.midterm2 as finalscore
FROM
    (select name, sum(grade) as total_grade from student group by name) as s
    INNER JOIN class ON s.name = class.studentname
    INNER JOIN exam on exam.studentname = s.name;

更一般的答案是聚合函数的结果当然可以在表达式中与其他值组合，但根据情况，这些其他值也可能必须是聚合函数的结果，或者可能需要添加更多GROUP BY子句的条件。

Answer 2

根据您的表格结构，您必须计算sum和student表之间的class，并将结果与exam表一起加入，如下所示。

试试如下。

SELECT 
    sc.Name, 
    (sc.GradeAndExtraCredit + exam.midterm1 + exam.midterm2) as FinalScore
FROM
    (SELECT Name, SUM(grade * extracredit) OVER (PARTITION BY Name) as GradeAndExtraCredit FROM student s INNER JOIN class c ON s.Name = c.StudentName) as sc
    INNER JOIN exam on exam.StudentName = sc.Name

添加其他数学表达式来聚合函数

2 个答案: