注意 ：|，； 是特殊符号，要用 "\\|", "\\;"来表示。
一行转多行
usertags 里面有很多项，每项之间以逗号分隔
create table tag_count2 as
select tag,count(gid) from (
select gid,tag from (select b.gid ,b.usertags from zhangb.gid_tags b group by b.gid,b.usertags) a
lateral view explode(split(a.usertags, ',')) t as tag
) p where substr(p.gid,1,7)='ANDROID' group by p.tag;
# 其中的 t 是把a表中的usertags 由一行变成多行后形成的新表的别称，是表的名称
导出数据：
insert overwrite local directory '/home/zhangb/tag_count'row format delimited fields terminated by '\t'
select distinct * from zhangb.tag_count
原格式：
gid1 abc,abd,abf
gid2 abc,snm
...
处理后输出格式：
gid1 abc
gid1 abd
gid1 abf
gid2 abc
gid2 snm
...
***多行转一行
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
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
