一、表架构

• student(sid,sname,sage,ssex) 学生表
• course(cid,cname,tid) 课程表
• sc(sid,cid,score) 成绩表
• teacher(tid,tname) 教师表

二 、建表sql语句

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for course
-- ----------------------------
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course`  (
  `cid` int(11) NOT NULL COMMENT '课程号',
  `cname` varchar(30) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL COMMENT '课程名',
  `tid` int(11) NULL DEFAULT NULL COMMENT '老师号',
  PRIMARY KEY (`cid`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci ROW_FORMAT = DYNAMIC;

-- ----------------------------
-- Records of course
-- ----------------------------
INSERT INTO `course` VALUES (3001, '英语', 1);
INSERT INTO `course` VALUES (3002, '数学', 2);
INSERT INTO `course` VALUES (3003, '物理', 3);
INSERT INTO `course` VALUES (3004, '语文', 4);

-- ----------------------------
-- Table structure for sc
-- ----------------------------
DROP TABLE IF EXISTS `sc`;
CREATE TABLE `sc`  (
  `sid` int(11) NOT NULL COMMENT '学生号',
  `cid` int(11) NOT NULL COMMENT '课程号',
  `score` int(11) NULL DEFAULT NULL COMMENT '成绩'
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci ROW_FORMAT = DYNAMIC;

-- ----------------------------
-- Records of sc
-- ----------------------------
INSERT INTO `sc` VALUES (101, 3001, 90);
INSERT INTO `sc` VALUES (102, 3001, 85);
INSERT INTO `sc` VALUES (103, 3001, 76);
INSERT INTO `sc` VALUES (104, 3002, 87);
INSERT INTO `sc` VALUES (105, 3001, 92);
INSERT INTO `sc` VALUES (101, 3002, 81);
INSERT INTO `sc`