我刚刚在Oracle SQL中启动了一个类,我们获得了创建3个实体和2个关系表的赋值。他给了我们这些领域并说我们觉得有必要加上:
Course: department, semester, maximumEnrolled
Instructor: firstName, lastName, ssn
Room: roomNumber, building
Teaches: instructor, course
Uses: course, room
当我创建表时,只有前4个工作,但我无法创建使用表。错误是:
ORA-02270:此列列表没有匹配的唯一键或主键。
这就是我所做的:
CREATE TABLE course
(course_id NUMBER(4) PRIMARY KEY,
courseName VARCHAR2(30) NOT NULL,
department VARCHAR2(50),
semester VARCHAR2(10),
maximumEnrolled NUMBER(36) NOT NULL);
CREATE TABLE room
(roomNo NUMBER(5) PRIMARY KEY,
building VARCHAR2(10));
CREATE TABLE instructor
(instructor_id NUMBER(6) PRIMARY KEY,
firstName VARCHAR2(20),
lastName VARCHAR2(30) NOT NULL
ssn NUMBER(9) NOT NULL);
CREATE TABLE teaches
(instructor_id NUMBER(5) NOT NULL,
course_id NUMBER(4) NOT NULL,
teachingCourse VARCHAR2(4) PRIMARY KEY,
CONSTRAINT instructor_fk FOREIGN KEY (instructor_id) REFERENCES instructor (instructor_id)
CONSTRAINT course_fk FOREIGN KEY (course_id) REFERENCES course (course_id));
CREATE TABLE uses
(course_id NUMBER(4) NOT NULL,
roomNo NUMBER(5) NOT NULL,
roomUse VARCHAR2(4) PRIMARY KEY,
CONSTRAINT course_fk FOREIGN KEY (course_id) REFERENCES course (course_id)
CONSTRAINT room_fk FOREIGN KEY (roomNo) REFERENCES room (roomNo));
我想也许问题是我在教学表中使用course_id作为FK所以我试过了:
CREATE TABLE uses
(roomUsage VARCHAR2(30) PRIMARY KEY,
roomNo NUMBER(5) NOT NULL,
courseName VARCHAR2(30) NOT NULL,
CONSTRAINT room_fk FOREIGN KEY (roomNo) REFERENCES room (roomNo),
CONSTRAINT course_fk FOREIGN KEY (courseName) REFERENCES course (courseName));
但它既没有奏效也给出了同样的错误。我做错了什么?
答案 0 :(得分:1)
您的某些表定义中缺少一些逗号(在lastname
中的instructor
之后,在最后两个表中的第一个fk之后)以及数据类型不匹配(大小) instructor_id
中的teaches
。此外,外键约束名称必须是唯一的 - 您正在course_fk
表中重用uses
- 重命名它。
更正的代码是:
CREATE TABLE course
(course_id NUMBER(4) PRIMARY KEY,
courseName VARCHAR2(30) NOT NULL,
department VARCHAR2(50),
semester VARCHAR2(10),
maximumEnrolled NUMBER(36) NOT NULL
);
CREATE TABLE room
(roomNo NUMBER(5) PRIMARY KEY,
building VARCHAR2(10));
CREATE TABLE instructor
(instructor_id NUMBER(6) PRIMARY KEY,
firstName VARCHAR2(20),
lastName VARCHAR2(30) NOT NULL,
ssn NUMBER(9) NOT NULL
);
CREATE TABLE teaches
(instructor_id NUMBER(6) NOT NULL,
course_id NUMBER(4) NOT NULL,
teachingCourse VARCHAR2(4) PRIMARY KEY,
CONSTRAINT instructor_fk FOREIGN KEY (instructor_id) REFERENCES instructor (instructor_id),
CONSTRAINT course_fk FOREIGN KEY (course_id) REFERENCES course (course_id)
);
CREATE TABLE uses
(course_id NUMBER(4) NOT NULL,
roomNo NUMBER(5) NOT NULL,
roomUse VARCHAR2(4) PRIMARY KEY,
CONSTRAINT course_fk2 FOREIGN KEY (course_id) REFERENCES course (course_id),
CONSTRAINT room_fk FOREIGN KEY (roomNo) REFERENCES room (roomNo)
);