一 竖表转横表
1. 学生表成绩表-竖表
2. 查询数据
select * from student;
3. 想要将数据显示为横表, 即如下形式
数据显示为横表 sql语句:
select name as '姓名',
max(case subject when '语文' then result else 0 end) '语文',
max(case subject when '数学' then result else 0 end) '数学',
max(case subject when '英语' then result else 0 end) '英语'
from student group by name;
二, 横表变竖表
1. 创建横表 - 学生成绩表
2. 查询数据
select * from student1;
3. 将横表数据转换为竖表的形式, 即如下形式:
对应的sql语句:
select*from
(
select 姓名 as Name , '语文' as Subject , 语文 as result from student1
union all
select 姓名 as Name , '数学' as Subject , 数学 as result from student1
union all
select 姓名 as Name , '物理' as Subject , 物理 as result from student1
) t
order by name;
三，横表变竖表的-关联查询
查询出结果的sql:
SELECT cp.person_name,cm.url from cm_person cp INNER JOIN cm_midia cm on cp.id_front_ukid = cm.id
UNION
SELECT cp.person_name,cm.url from cm_person cp INNER JOIN cm_midia cm on cp.id_back_ukid = cm.id
UNION
SELECT cp.person_name,cm.url from cm_person cp INNER JOIN cm_midia cm on cp.id_header_ukid = cm.id;
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