SQL查询以查找有关未在特定班级注册的学生的所有信息

Question

假设我有三个表Student，Class，Student_Class（链接表）。

Table:Student
Student_ID
FirstName
LastName

Table:Class
Class_ID
Class_name

Table:Student_Class (Linking Table)
StudentClass_ID
Class_ID
Student_ID

给定一个特定的Class_ID，我想了解有关未注册该特定班级的学生的所有信息。

我尝试了以下操作，但不起作用。 可以说我尝试输入班级ID = 3

SELECT DISTINCT Student.* 
FROM Student 
INNER JOIN Student_Class 
    ON Student.Student_ID = Student_Class.Student_ID 
WHERE ((NOT (Student_Class.Class_ID)= 3))

Answer 1

流

1. 匹配所有学生和所有班级

Student INNER JOIN Student_Class ON (Student.Student_ID = Student_Class.Student_ID)

2. 拒绝特定班级的学生（示例3）

(Student_Class.Class_ID <> 3)

查询：

SELECT Student.* 
  FROM Student INNER JOIN Student_Class 
    ON (Student.Student_ID = Student_Class.Student_ID)
 WHERE (Student_Class.Class_ID <> 3);

为了让所有学生都没有上课，请尝试以下操作：

SELECT Student.*
  FROM
       (
        SELECT Student.*
             , Student_Class.Class_ID
          FROM Student LEFT JOIN Student_Class ON Student.Student_ID = Student_Class.Student_ID
         WHERE ((Student_Class.Class_ID <> 3) OR (Student_Class.Class_ID IS NULL))
        ) Student LEFT JOIN Class ON Student.Class_ID = Class.Class_ID
;

数据：

结果：

Answer 2

下面的查询将显示所有未参加1个或更多课程的学生，包括班级名称。

SELECT Student.Student_ID, Student.FirstName, Student.LastName, 
Class.Class_ID, Class.Class_name
FROM Class, Student
WHERE NOT EXISTS
(
SELECT *
FROM Student_Class
WHERE Student_Class.Student_ID = Student.Student_ID AND   
Student_Class.Class_ID = Class.Class_ID

）