##[函数]Hive中行列转换(行转列)

Hive中行列转换 - 菠萝大数据梦工厂（Free World） - 博客频道 - CSDN.NET http://blog.csdn.net/jiangshouzhuang/article/details/46810529

1、演示多列转为单行
数据文件及内容： student.txt
xiaoming|english|92.0
xiaoming|chinese|98.0
xiaoming|math|89.5
huahua|chinese|80.0
huahua|math|89.5

创建表studnet：
create table student(name string,subject string,score decimal(4,1))
row format delimited
fields terminated by '|';

导入数据：
load data local inpath '/home/hadoop/hivetestdata/student.txt' into table student;

列转为行演示：
hive (hive)> select name,concat_ws(',',collect_set(subject)) from student group by name;
huahua chinese,math
xiaoming english,chinese,math

hive (hive)> select name,concat_ws(',',collect_set(concat(subject,'=',score))) from student group by name;
huahua chinese=80,math=89.5
xiaoming english=92,chinese=98,math=89.5

2、演示单行转为多列
数据文件及内容：student2.txt
huahua|chinese=80,math=89.5
xiaoming|english=92,chinese=98,math=89.5

创建表：
create table student2(name string,subject_score_list string)
row format delimited
fields terminated by '|';
导入数据：
load data local inpath '/home/hadoop/hivetestdata/student2.txt' into table student2;

行转为列演示：
hive (hive)> select * from student2;
student2.name student2.subject_score_list
huahua chinese=80,math=89.5
xiaoming english=92,chinese=98,math=89.5

hive (hive)> select name, subject_list from student2 stu2 lateral view explode(split(stu2.subject_score_list,','))stu_subj as subject_list; ----别名一定不要忘记
huahua chinese=80
huahua math=89.5
xiaoming english=92
xiaoming chinese=98
xiaoming math=89.5