示例(mysql)
原表：
表名 :user
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name | course | grade
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zhangsan | Java | 70
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zhangsan | C++ | 80
----------------------------------------
lisi | java | 90
----------------------------------------
lisi | C# | 60
----------------------------------------
用一條 SQL 語句得到如下形式：
----------------------------------------
name | java | C++ | C#
----------------------------------------
zhangsan | 70 | 80 | null
----------------------------------------
lisi | 90 | null | 60
----------------------------------------
方案1
select name,
sum(case when course='java' then grade end) as java,
sum(case when course='C++' then grade end) as C++,
sum(case when course='C#' then grade end) as C#
from test group by name
方案2
select distinct c.`name` AS name,
(select grade from test where name = c.`name` and course = 'java' )as java,
(select grade from test where name = c.`name` and course = 'C++' )as C++,
(select grade from test where name = c.`name` and course = 'C#' )as C#
from test c
