Hive知识点总结（二）
Hive知识点总结（一）地址：点击查看
3、数据类型
3.1、数字类型
和java数字类型一样：
TINYINT (1-byte signed integer, from -128 to 127)
SMALLINT (2-byte signed integer, from -32,768 to 32,767)
INT/INTEGER (4-byte signed integer, from -2,147,483,648 to 2,147,483,647)
BIGINT (8-byte signed integer, from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807)
FLOAT (4-byte single precision floating point number)
DOUBLE (8-byte double precision floating point number)
3.2、日期时间类型
TIMESTAMP (Note: Only available starting with Hive 0.8.0)
DATE (Note: Only available starting with Hive 0.12.0)
3.3、字符串类型
STRING
VARCHAR (Note: Only available starting with Hive 0.12.0)
CHAR (Note: Only available starting with Hive 0.13.0)
3.4、混杂类型
BOOLEAN
BINARY (Note: Only available starting with Hive 0.8.0)
3.5、复合类型
3.5.1、array数组类型
arrays: ARRAY
示例：array类型的应用
假如有如下数据需要用hive的表去映射：
战狼2,吴京:吴刚:龙母,2017-08-16
三生三世十里桃花,刘亦菲:痒痒,2017-08-20
设想：如果主演信息用一个数组来映射比较方便
建表：
create table t_movie(moive_name string,actors array,first_show date)
row format delimited fields terminated by ','
collection items terminated by ':';
导入数据：
load data local inpath '/root/movie.dat' into table t_movie;
查询：
select * from t_movie;
select moive_name,actors[0] from t_movie;
select moive_name,actors from t_movie where array_contains(actors,'吴刚');
select moive_name,size(actors) from t_movie; 3.5.2、map类型
maps: MAP
假如有以下数据：
1,zhangsan,father:xiaoming#mother:xiaohuang#brother:xiaoxu,28
2,lisi,father:mayun#mother:huangyi#brother:guanyu,22
3,wangwu,father:wangjianlin#mother:ruhua#sister:jingtian,29
4,mayun,father:mayongzhen#mother:angelababy,26
可以用一个map类型来对上述数据中的家庭成员进行描述
建表语句：
create table t_person(id int,name string,family_members map,age int)
row format delimited fields terminated by ','
collection items terminated by '#'
map keys terminated by ':';
查询
select * from t_person;
## 取map字段的指定key的值
select id,name,family_members['father'] as father from t_person;
## 取map字段的所有key
select id,name,map_keys(family_members) as relation from t_person;
## 取map字段的所有value
select id,name,map_values(family_members) from t_person;
select id,name,map_values(family_members)[0] from t_person;
## 综合：查询有brother的用户信息
select id,name,father
from
(select id,name,family_members['brother'] as father from t_person) tmp
where father is not null; 3.5.3、struct类型
structs: STRUCT
1)假如有如下数据：
1,zhangsan,18:male:beijing
2,lisi,28:female:shanghai
其中的用户信息包含：年龄：整数，性别：字符串，地址：字符串
设想用一个字段来描述整个用户信息，可以采用struct
建表：
create table t_person_struct(id int,name string,info struct)
row format delimited fields terminated by ','
collection items terminated by ':';
查询
select * from t_person_struct;
select id,name,info.age from t_person_struct; 4、修改表定义
只修改Hive元数据，不会触动表中的数据，用户需要确定实际的数据布局符合元数据的定义。
修改表名：
ALTER TABLE table_name RENAME TO new_table_name
示例：alter table t_1 rename to t_x;
修改分区名：
alter table t_partition partition(department='xiangsheng',sex='male',howold=20) rename to partition(department='1',sex='1',howold=20);
添加分区：
alter table t_partition add partition (department='2',sex='0',howold=40);
删除分区：
alter table t_partition drop partition (department='2',sex='2',howold=24);
修改表的文件格式定义：
ALTER TABLE table_name [PARTITION partitionSpec] SET FILEFORMAT file_format
alter table t_partition partition(department='2',sex='0',howold=40 ) set fileformat sequencefile;
修改列名定义：
ALTER TABLE table_name CHANGE [COLUMN] col_old_name col_new_name column_type [COMMENTcol_comment] [FIRST|(AFTER column_name)]
alter table t_user change price jiage float first;
增加/替换列：
ALTER TABLE table_name ADD|REPLACE COLUMNS (col_name data_type[COMMENT col_comment], ...)
alter table t_user add columns (sex string,addr string);
alter table t_user replace columns (id string,age int,price float);