Question

以下是我的查询基本上有一个学生分会表，其中包含学生课程信息，此表除了课程描述外还有我需要的一切。这包含在课程表中。出于某种原因，我似乎只能从studentsection表中获取条目，我尝试的每个查询都从课程表中获取所有内容。非常感谢任何帮助！

select distinct studentid
              , s.deptnum
              , s.coursenum
              , coursedesc
              , sectionnum
              , quarter
              , grade 
           from studentsection c
           left 
           join course c
             on s.deptnum = c.deptnum 
          where exists( select deptnum from course) 
          order 
             by studentid
              , quarter
              , grade;

以下是我的表格定义：

create table StudentSection(
    studentID int,
    deptNum char(4),
    courseNum char(3),
    sectionNum char(2),
    quarter char(3),
    grade varchar(1),
    constraint studentSection_PK primary key(studentID, deptNum, courseNum, sectionNum, quarter),
    constraint studentSection_section_FK foreign key (deptNum, courseNum, sectionNum, quarter) references Section(deptNum, courseNum, sectionNum, quarter)
)

CREATE TABLE Course (
    deptNum    char(4),
    courseNum  char(3),
    courseDesc varchar(50) NOT NULL,
    creditHrs integer,
    CONSTRAINT course_PK PRIMARY KEY (deptNum, courseNum),
    CONSTRAINT course_department_FK FOREIGN KEY (deptNum) REFERENCES department(deptNum))

CREATE TABLE Section (
    deptNum     char(4),
    courseNum   char(3),
    sectionNum  char(2),
    quarter     char(3),
    instructor  varchar(20),
    CONSTRAINT section_PK PRIMARY KEY (deptNum, courseNum, sectionNum, quarter),
    CONSTRAINT section_course_FK FOREIGN KEY (deptNum, courseNum) REFERENCES course(deptNum, courseNum));

Answer 1

我不确定我的问题是否正确，但您是否尝试了inner join？

mysql加入没有得到理想的结果

1 个答案: