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下面是我的查詢基本上那裏有一個包含學生課程信息的studentsection表,這張表除了課程描述之外還有我需要的一切。這包含在課程表中。出於某種原因,我似乎無法只從studentsection表中獲取條目,我嘗試的每個查詢都會從課程表中獲取所有內容。任何幫助深表感謝!mysql加入不到期望的結果
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;
這裏是我的表定義:
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));
您是否加入正確的領域? 'deptnum'是'course'的'PRIMARY KEY'嗎?你能否發表你的表格定義? – Quassnoi 2011-05-06 11:31:27