msyql笔记

CREATE TABLE class (
  cid int(11) NOT NULL AUTO_INCREMENT,
  caption varchar(32) NOT NULL,
  PRIMARY KEY (cid)
) ENGINE=InnoDB CHARSET=utf8;
CREATE TABLE student(
  sid int(11) NOT NULL AUTO_INCREMENT,
  gender char(1) NOT NULL,
  class_id int(11) NOT NULL,
  sname varchar(32) NOT NULL,
  PRIMARY KEY (sid),
  KEY fk_class (class_id),
  CONSTRAINT fk_class FOREIGN KEY (class_id) REFERENCES class (cid)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE teacher(
  tid int(11) NOT NULL AUTO_INCREMENT,
  tname varchar(32) NOT NULL,
  PRIMARY KEY (tid)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE course(
  cid int(11) NOT NULL AUTO_INCREMENT,
  cname varchar(32) NOT NULL,
  teacher_id int(11) NOT NULL,
  PRIMARY KEY (cid),
  KEY fk_course_teacher (teacher_id), #创建索引并加约束
  CONSTRAINT fk_course_teacher FOREIGN KEY (teacher_id) REFERENCES teacher (tid)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE score (
  sid int(11) NOT NULL AUTO_INCREMENT,
  student_id int(11) NOT NULL,
  course_id int(11) NOT NULL,
  num int(11) NOT NULL,
  PRIMARY KEY (sid),
  KEY fk_score_student (student_id),
  KEY fk_score_course (course_id),
  CONSTRAINT fk_score_course FOREIGN KEY (course_id) REFERENCES course (cid),
  CONSTRAINT fk_score_student FOREIGN KEY (student_id) REFERENCES student(sid)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO class VALUES
(1, '三年二班'),
(2, '三年三班'),
(3, '一年二班'),
(4, '二年九班');
INSERT INTO student VALUES
(1, '男', 1, '理解'),
(2, '女', 1, '钢蛋'),
(3, '男', 1, '张三'),
(4, '男', 1, '张一'),
(5, '女', 1, '张二'),
(6, '男', 1, '张四'),
(7, '女', 2, '铁锤'),
(8, '男', 2, '李三'),
(9, '男', 2, '李一'),
(10, '女', 2, '李二'),
(11, '男', 2, '李四'),
(12, '女', 3, '如花'),
(13, '男', 3, '刘三'),
(14, '男', 3, '刘一'),
(15, '女', 3, '刘二'),
(16, '男', 3, '刘四');
INSERT INTO teacher VALUES
(1, '张磊老师'),
(2, '李平老师'),
(3, '刘海燕老师'),
(4, '朱云海老师'),
(5, '李杰老师');
INSERT INTO course VALUES
(1, '生物', 1),
(2, '物理', 2),
(3, '体育', 3),
(4, '美术', 2);
INSERT INTO score VALUES
(1, 1, 1, 10),
(2, 1, 2, 9),
(5, 1, 4, 66),
(6, 2, 1, 8),
(8, 2, 3, 68),
(9, 2, 4, 99),
(10, 3, 1, 77),
(11, 3, 2, 66),
(12, 3, 3, 87),
(13, 3, 4, 99),
(14, 4, 1, 79),
(15, 4, 2, 11),
(16, 4, 3, 67),
(17, 4, 4, 100),
(18, 5, 1, 79),
(19, 5, 2, 11),
(20, 5, 3, 67),
(21, 5, 4, 100),
(22, 6, 1, 9),
(23, 6, 2, 100),
(24, 6, 3, 67),
(25, 6, 4, 100),
(26, 7, 1, 9),
(27, 7, 2, 100),
(28, 7, 3, 67),
(29, 7, 4, 88),
(30, 8, 1, 9),
(31, 8, 2, 100),
(32, 8, 3, 67),
(33, 8, 4, 88),
(34, 9, 1, 91),
(35, 9, 2, 88),
(36, 9, 3, 67),
(37, 9, 4, 22),
(38, 10, 1, 90),
(39, 10, 2, 77),
(40, 10, 3, 43),
(41, 10, 4, 87),
(42, 11, 1, 90),
(43, 11, 2, 77),
(44, 11, 3, 43),
(45, 11, 4, 87),
(46, 12, 1, 90),
(47, 12, 2, 77),
(48, 12, 3, 43),
(49, 12, 4, 87),
(52, 13, 3, 87);

1.KEY fk_course_teacher (teacher_id),表示创建索引fk_course_teacher，类型是normal。并添加约束

2.在关联表的时候需要先创建好。

3.在删除的时候要先删除关联表，否则出错。

4.CONSTRAINT fk_class FOREIGN KEY (class_id) REFERENCES class (cid) ，添加外键约束FOREIGN KEY (class_id) REFERENCES class (cid)表示本表的class_id字段外联class表的cid字段。class如果不提前创建好就出出错。

后续。。。