前言： mysql的行轉列並沒有mssql中的pivot

測試資料：

DROP TABLE IF EXISTS `mytest`;
CREATE TABLE `mytest` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `class` varchar(255) DEFAULT NULL,
  `score` double DEFAULT NULL,
  `userid` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=latin1;

INSERT INTO `mytest` VALUES ('1', 'math', '90', '1');
INSERT INTO `mytest` VALUES ('2', 'english', '90', '1');
INSERT INTO `mytest` VALUES ('3', 'computer', '80', '1');
INSERT INTO `mytest` VALUES ('4', 'sports', '90', '1');
INSERT INTO `mytest` VALUES ('5', 'math', '80', '2');
INSERT INTO `mytest` VALUES ('6', 'english', '85', '2');
INSERT INTO `mytest` VALUES ('7', 'computer', '100', '2');
 

語句：

SET @EE='';
    SELECT @EE:=CONCAT(@EE,'SUM(IF(class=\'',class,'\'',',score,0)) AS ',class,',') 
    FROM (SELECT DISTINCT class FROM mytest) A;
SET @QQ=CONCAT('SELECT mytest.userid AS columnA,',LEFT(@EE,LENGTH(@EE)-1),' 
    FROM mytest GROUP BY userid');
PREPARE stmt2 FROM @QQ;

PS: 如果將這塊sql封裝成儲存過程，會返回2個結果集，一個sql語句，還有一個查詢結果。
所以如果是儲存過程的話，推薦這麼實用：

#drop PROCEDURE sp_mytest

create PROCEDURE sp_mytest()
begin 
SET @EE='';
    SELECT b.* into @EE from ( SELECT @EE:=CONCAT(@EE,'SUM(IF(class=\'',class,'\'',',score,0)) AS ',class,',') col
    FROM (SELECT DISTINCT class FROM mytest) A) b ORDER BY b.col desc limit 0,1 ;
SET @QQ=CONCAT('SELECT mytest.userid AS columnA,',LEFT(@EE,LENGTH(@EE)-1),' 
    FROM mytest GROUP BY userid');
PREPARE stmt2 FROM @QQ;
EXECUTE stmt2;
end


call sp_mytest()