Question

mysql一张表中外键键和主键可以相连吗?

-- //外键约束
DROP TABLE subjectinfo;
CREATE TABLE IF NOT EXISTS subjectinfo(
subId INT PRIMARY KEY,
subName VARCHAR(50) NOT NULL,
classhours INT NOT NULL,
gid INT NOT NULL
);
select * from subjectinfo;
ALTER TABLE subjectinfo
ADD CONSTRAINT FK_gid FOREIGN KEY(gid) REFERENCES subjectinfo(subId);
INSERT INTO subjectinfo VALUES(1,'Java编程基础',10,1);
INSERT INTO subjectinfo VALUES(2,'T-SQL数据库操作',11,2);
INSERT INTO subjectinfo VALUES(3,'WEB前段基础',12,3);
INSERT INTO subjectinfo VALUES(4,'jquery框架',13,4);
INSERT INTO subjectinfo VALUES(5,'AI基础',14,5);
INSERT INTO subjectinfo VALUES(6,'3D动画',15,6);

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Answer 1

应该是可以的啊. mysql> CREATE TABLE course ( -> course_NO INT PRIMARY KEY -> ); Query OK, 0 rows affected (0.19 sec) mysql> mysql> CREATE TABLE teacher ( -> teacher_ID INT PRIMARY KEY -> ); Query OK, 0 rows affected (0.08 sec) mysql> CREATE TABLE temp ( -> course_NO INT, -> teacher_ID INT, -> foreign key(course_NO) references course(course_NO), -> foreign key(teacher_ID)references teacher (teacher_ID), -> primary key(course_NO,teacher_ID) -> ); Query OK, 0 rows affected (0.10 sec)

Answer 2

create table employee
(
zno varchar(6) primary key comment '职工号',
zname varchar(30) not null comment '姓名',
sex varchar(2) comment '性别',
title varchar(10) comment '职称',
leader Varchar(6) comment '领导',
foreign key (leader) references employee(zno)
);