The database column switch, turn the column row

The database column switch, turn the column row

Create a table

# 建表语句
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= Utfa8;

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adding data

# Add data
 INSERT  INTO TEST_TB_GRADE ( USER_NAME , COURSE, SCORE)   values 
( "Joe Smith", "Mathematics", 34 ), 
( "Joe Smith", "Chinese", 58 ), 
( "Joe Smith", "English" 58 ), 
( "John Doe", "Mathematics", 45 ), 
( "John Doe", "Chinese", 87 ), 
( "John Doe", "English", 45 ), 
( "Wang five", "math " 76 ), 
(" Wang five "," Chinese ", 34 ), 
(" Wang five "," English ", 89 );

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SQL column switch

# Column switch
 the SELECT  user_name ,
     MAX ( the CASE Course, the WHEN  ' mathematics '  THEN Score ELSE  0  END ) mathematics,
     MAX ( the CASE Course, the WHEN  ' language '  THEN Score ELSE  0  END ) language,
     MAX ( the CASE Course, the WHEN  ' English '  THEN Score ELSE  0  END ) English
 the FROM test_tb_grade
 the GROUP BY USER_NAME;

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Column switch changes

Line transfer column

Need to first convert the data into the result table result

Results Table # Create a table
 the CREATE  TABLE `result` ( 
  ` USER_NAME ` VARCHAR ( 20 is ) the DEFAULT  NULL , 
  ` COURSE` VARCHAR ( 20 is ) the DEFAULT  NULL , 
  `SCORE` a float  the DEFAULT  ' 0 ' 
) ENGINE = the InnoDB the AUTO_INCREMENT = . 1  the DEFAULT the CHARSET = UTF8 ; 
# query results to the data transferred to the table 
INSERT  iNTO result
 the SELECT  USER_NAME ,
     MAX (The CASE Course, the WHEN  ' mathematics '  THEN Score ELSE  0  END ) mathematics,
     MAX ( the CASE Course, the WHEN  ' language '  THEN Score ELSE  0  END ) language,
     MAX ( the CASE Course, the WHEN  ' English '  THEN Score ELSE  0  END ) English
 the FROM test_tb_grade
 the GROUP  BY  USER_NAME ;

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After then turn the column row

# Line switch columns
 the SELECT  USER_NAME , ' language ' COURSE, MAX (language) AS Score from the Result the GROUP  by  USER_NAME  of Union  ALL 
the SELECT  USER_NAME , ' mathematics ' COURSE, MAX (mathematics) AS Score from the Result   the GROUP  by  USER_NAME  of Union  ALL 
the SELECT  USER_NAME , ' English ' COURSE, MAX (English) AS Score from result  GROUP by USER_NAME

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Changes turn row columns