mysql指令碼，新建表和理清表之間的聯絡

/*

Navicat MySQL Data Transfer

Source Server         : localhost

Source Server Version : 50520

Source Host           : localhost:3306

Source Database       : gupao

Target Server Type    : MYSQL

Target Server Version : 50520

File Encoding         : 65001

Date: 2018-07-24 22:42:54

*/

SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------

-- Table structure for baoming

-- ----------------------------

DROP TABLE IF EXISTS `baoming`;

CREATE TABLE `baoming` (

  `id` int(11) NOT NULL AUTO_INCREMENT,

  `sid` int(11) DEFAULT NULL,

  `kid` int(11) DEFAULT NULL,

  PRIMARY KEY (`id`)

) ENGINE=InnoDB AUTO_INCREMENT=12 DEFAULT CHARSET=utf8;

-- ----------------------------

-- Records of baoming

-- ----------------------------

INSERT INTO `baoming` VALUES ('1', '1', '1');

INSERT INTO `baoming` VALUES ('2', '2', '1');

INSERT INTO `baoming` VALUES ('3', '3', '1');

INSERT INTO `baoming` VALUES ('4', '4', '2');

INSERT INTO `baoming` VALUES ('5', '5', '2');

INSERT INTO `baoming` VALUES ('6', '6', '2');

INSERT INTO `baoming` VALUES ('7', '7', '3');

INSERT INTO `baoming` VALUES ('9', '1', '3');

INSERT INTO `baoming` VALUES ('10', '3', '3');

INSERT INTO `baoming` VALUES ('11', '5', '3');

-- ----------------------------

-- Table structure for class

-- ----------------------------

DROP TABLE IF EXISTS `class`;

CREATE TABLE `class` (

  `cid` int(11) NOT NULL AUTO_INCREMENT,

  `level` int(11) DEFAULT NULL,

  `name` varchar(255) DEFAULT NULL,

  PRIMARY KEY (`cid`)

) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

-- ----------------------------

-- Records of class

-- ----------------------------

INSERT INTO `class` VALUES ('1', '1', '班級1');

INSERT INTO `class` VALUES ('2', '1', '班級2');

INSERT INTO `class` VALUES ('3', '2', '班級3');

INSERT INTO `class` VALUES ('4', '3', '班級4');

-- ----------------------------

-- Table structure for ke

-- ----------------------------

DROP TABLE IF EXISTS `ke`;

CREATE TABLE `ke` (

  `kid` int(11) NOT NULL AUTO_INCREMENT,

  `name` varchar(255) DEFAULT NULL,

  `tid` int(11) DEFAULT NULL,

  PRIMARY KEY (`kid`)

) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8;

-- ----------------------------

-- Records of ke

-- ----------------------------

INSERT INTO `ke` VALUES ('1', '課程1', '2');

INSERT INTO `ke` VALUES ('2', '課程2', '1');

INSERT INTO `ke` VALUES ('3', '課程3', '5');

INSERT INTO `ke` VALUES ('4', '課程4', '5');

INSERT INTO `ke` VALUES ('5', '課程0', '0');

INSERT INTO `ke` VALUES ('6', '課程', null);

-- ----------------------------

-- Table structure for student

-- ----------------------------

DROP TABLE IF EXISTS `student`;

CREATE TABLE `student` (

  `sid` int(11) NOT NULL AUTO_INCREMENT,

  `name` varchar(255) DEFAULT NULL,

  `sex` int(11) DEFAULT '1',

  `cid` int(11) DEFAULT NULL,

  PRIMARY KEY (`sid`)

) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8;

-- ----------------------------

-- Records of student

-- ----------------------------

INSERT INTO `student` VALUES ('1', '學生1', '1', '1');

INSERT INTO `student` VALUES ('2', '學生2', '1', '1');

INSERT INTO `student` VALUES ('3', '學生3', '2', '1');

INSERT INTO `student` VALUES ('4', '學生4', '2', '1');

INSERT INTO `student` VALUES ('5', '學生5', '1', '2');

INSERT INTO `student` VALUES ('6', '學生6', '1', '2');

INSERT INTO `student` VALUES ('7', '學生7', '2', '2');

INSERT INTO `student` VALUES ('8', '學生8', '2', '2');

INSERT INTO `student` VALUES ('9', '學生9', '1', '3');

INSERT INTO `student` VALUES ('10', '學生0', '1', '0');

-- ----------------------------

-- Table structure for teacher

-- ----------------------------

DROP TABLE IF EXISTS `teacher`;

CREATE TABLE `teacher` (

  `tid` int(11) NOT NULL AUTO_INCREMENT,

  `name` varchar(255) DEFAULT NULL,

  `sex` int(11) DEFAULT '1',

  PRIMARY KEY (`tid`)

) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8;

-- ----------------------------

-- Records of teacher

-- ----------------------------

INSERT INTO `teacher` VALUES ('1', '教授1', '1');

INSERT INTO `teacher` VALUES ('2', '教授2', '1');

INSERT INTO `teacher` VALUES ('3', '教授3', '2');

INSERT INTO `teacher` VALUES ('4', '教授4', '2');

INSERT INTO `teacher` VALUES ('5', '大教授', '1');

INSERT INTO `teacher` VALUES ('6', '助教', '2');

在上課的老師

SELECT DISTINCT t.name FROM ke

JOIN  teacher AS t ON  ke.tid=t.tid

  老師和學生的對應關係

SELECT * FROM ke

JOIN  teacher AS t ON  ke.tid=t.tid

JOIN  baoming AS b ON ke.kid=b.kid

JOIN student AS s ON b.sid=s.sid