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纵表结构 TableA

Name|Course|Grade
:--|:--|:--
张三|语文|75
张三|数学|80
张三|英语|90
李四|语文|95
李四|数学|55

横表结构 TableB

Name|语文|数学|英语
:--|:--|:--|:--
张三|75|80|90
李四|95|55|0

先理解：
select Name，
(case Course when '语文' then Grade else 0 end) as 语文，
(case Course when '数学' then Grade else 0 end) as 数学，
(case Course when '英语' then Grade else 0 end) as 英语
from TableA

然后理解标准答案：

select Name，
sum(case Course when '语文' then Grade else 0 end) as 语文，
sum(case Course when '数学' then Grade else 0 end) as 数学，
sum(case Course when '英语' then Grade else 0 end) as 英语
from TableA
group by Name

SELECT   姓名,'语文'   AS     科目,语文   AS   成绩   FROM   TEST_H2Z   UNION   ALL  
SELECT   姓名,'数学'   AS     科目,数学   AS   成绩   FROM   TEST_H2Z   UNION   ALL  
SELECT   姓名,'英语'   AS     科目,英语   AS   成绩   FROM   TEST_H2Z ORDER BY 姓名,科目 DESC;