mysql 行转列和列转行实例详解

mysql/' target='_blank'>mysql行转列、列转行

语句不难，不做多余解释了，看语句时，从内往外一句一句剖析

行转列

有如图所示的表，现在希望查询的结果将行转成列

建表语句如下：

CREATE TABLE `TEST_TB_GRADE` ( `ID` int(10) NOT NULL AUTO_INCREMENT, `USER_NAME` varchar(20) DEFAULT NULL, `COURSE` varchar(20) DEFAULT NULL, `SCORE` float DEFAULT '0', PRIMARY KEY (`ID`)) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

insert into TEST_TB_GRADE(USER_NAME, COURSE, SCORE) values("张三", "数学", 34),("张三", "语文", 58),("张三", "英语", 58),("李四", "数学", 45),("李四", "语文", 87),("李四", "英语", 45),("王五", "数学", 76),("王五", "语文", 34),("王五", "英语", 89);

查询语句：

此处用之所以用MAX是为了将无数据的点设为0，防止出现NULL

SELECT user_name ,  MAX(CASE course WHEN '数学' THEN score ELSE 0 END ) 数学,  MAX(CASE course WHEN '语文' THEN score ELSE 0 END ) 语文,  MAX(CASE course WHEN '英语' THEN score ELSE 0 END ) 英语FROM test_tb_gradeGROUP BY USER_NAME;

结果展示：

列转行

有如图所示的表，现在希望查询的结果将列成行

建表语句如下：

CREATE TABLE `TEST_TB_GRADE2` ( `ID` int(10) NOT NULL AUTO_INCREMENT, `USER_NAME` varchar(20) DEFAULT NULL, `CN_SCORE` float DEFAULT NULL, `MATH_SCORE` float DEFAULT NULL, `EN_SCORE` float DEFAULT '0', PRIMARY KEY (`ID`)) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

insert into TEST_TB_GRADE2(USER_NAME, CN_SCORE, MATH_SCORE, EN_SCORE) values("张三", 34, 58, 58),("李四", 45, 87, 45),("王五", 76, 34, 89);

查询语句：

select user_name, '语文' COURSE , CN_SCORE as SCORE from test_tb_grade2union select user_name, '数学' COURSE, MATH_SCORE as SCORE from test_tb_grade2union select user_name, '英语' COURSE, EN_SCORE as SCORE from test_tb_grade2order by user_name,COURSE;

结果展示：

感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！