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：
1 2 3 4 5 6 7 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; 1 2 3 4 5 6 7 8 9 10 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
1 2 3 4 5 6 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_grade GROUP 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：
1 2 3 4 5 6 7 8 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; 1 2 3 4 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：
1 2 3 4 select user_name, '语文' COURSE , CN_SCORE as SCORE from test_tb_grade2 union select user_name, '数学' COURSE, MATH_SCORE as SCORE from test_tb_grade2 union select user_name, '英语' COURSE, EN_SCORE as SCORE from test_tb_grade2 order by user_name,COURSE;结果展示：
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