How mysql converts a column value to a column

Copy codeThe Code is as follows:
-- Create a database
Create table 'rate '(
'Uname' VARCHAR (300 ),
'Object' VARCHAR (300 ),
'Score 'varchar (300)
);

-- Insert data
Insert into test. rate (uname, object, score)
VALUES ('aaa', 'China', '67 '),
('Aaa', 'Math', '89 '),
('Aaa', 'Physical ', '89 '),
('Bbb ', 'China', '67 '),
('Bbb ', 'Math', '75 '),
('Bbb ', 'Physical', '89 ');

-- Query
Select distinct uname AS 'name ',
SUM (CASE object
WHEN 'China' THEN score END) AS 'China ',
SUM (CASE object
WHEN 'Math' THEN score END) AS 'mate ',
SUM (CASE object
WHEN 'physical 'then score END) AS 'physical 'FROM rate group by uname;