sql 纵表转横表

DROP TABLE IF EXISTS `course`;
CREATE TABLE `course` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of course
-- ----------------------------
INSERT INTO `course` VALUES ('1', '语文');
INSERT INTO `course` VALUES ('2', '数学');
INSERT INTO `course` VALUES ('3', '英语');

-- ----------------------------
-- Table structure for score
-- ----------------------------
DROP TABLE IF EXISTS `score`;
CREATE TABLE `score` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`sid` int(11) DEFAULT NULL,
`cid` int(11) DEFAULT NULL,
`score` int(11) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=22 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of score
-- ----------------------------
INSERT INTO `score` VALUES ('1', '1', '1', '60');
INSERT INTO `score` VALUES ('2', '1', '2', '87');
INSERT INTO `score` VALUES ('3', '1', '3', '64');
INSERT INTO `score` VALUES ('4', '2', '1', '76');
INSERT INTO `score` VALUES ('5', '2', '2', '98');
INSERT INTO `score` VALUES ('6', '2', '3', '73');
INSERT INTO `score` VALUES ('7', '3', '1', '22');
INSERT INTO `score` VALUES ('8', '3', '2', '62');
INSERT INTO `score` VALUES ('9', '3', '3', '48');
INSERT INTO `score` VALUES ('10', '4', '1', '77');
INSERT INTO `score` VALUES ('11', '4', '2', '47');
INSERT INTO `score` VALUES ('12', '4', '3', '65');
INSERT INTO `score` VALUES ('13', '5', '1', '84');
INSERT INTO `score` VALUES ('14', '5', '2', '88');
INSERT INTO `score` VALUES ('15', '5', '3', '75');
INSERT INTO `score` VALUES ('16', '6', '1', '98');
INSERT INTO `score` VALUES ('17', '6', '2', '76');
INSERT INTO `score` VALUES ('18', '6', '3', '66');
INSERT INTO `score` VALUES ('19', '7', '1', '67');
INSERT INTO `score` VALUES ('20', '7', '2', '93');
INSERT INTO `score` VALUES ('21', '7', '3', '74');

-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(255) DEFAULT NULL,
`age` int(11) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES ('1', '张三', '12');
INSERT INTO `student` VALUES ('2', '李四', '12');
INSERT INTO `student` VALUES ('3', '王五', '12');
INSERT INTO `student` VALUES ('4', '赵柳', '12');
INSERT INTO `student` VALUES ('5', '田七', null);

SELECT
    s.username,
    SUM(
        CASE s.`name`
        WHEN '语文' THEN
            s.score
        END
    ) AS yuwne,
    SUM(
        CASE s.`name`
        WHEN '语文' THEN
            s.score
        END
    ) AS shuxue,
    SUM(
        CASE s.`name`
        WHEN '语文' THEN
            s.score
        END
    ) AS yinyu
FROM
    (
        SELECT
            student.username,
            course.`name`,
            score.score
        FROM
            score
        JOIN student ON student.id = score.sid
        JOIN course ON course.id = score.cid
    ) s
GROUP BY
    s.username