hive hive窗口打印库和表头、复杂类型ARRAY、MAP 和 STRUCT的定义和使用

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1. hive窗口打印库和表头

  在hive-site.xml中加入如下两个配置:

<property>
    <name>hive.cli.print.header</name>
    <value>true</value>
</property>
<property>
    <name>hive.cli.print.current.db</name>
    <value>true</value>
</property>

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2. hive支持的类型

data type文档

Complex Types
arrays: ARRAY<data_type> (Note: negative values and non-constant expressions are allowed as of Hive 0.14.)
maps: MAP<primitive_type, data_type> (Note: negative values and non-constant expressions are allowed as of Hive 0.14.)
structs: STRUCT<col_name : data_type [COMMENT col_comment], …>
union: UNIONTYPE<data_type, data_type, …> (Note: Only available starting with Hive 0.7.0.)

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3. 复杂类型

3.1 ARRAY、MAP 和 STRUCT

数据类型	描述	语法
STRUCT	通过点符号访问元素内容。如列的数据类型是struct<street:string,city:string>,那么第1个元素可以通过字段名.street来引用	STRUCT<col_name : data_type [COMMENT col_comment], ...>
MAP	MAP是一组键值对元组集合，使用数组表示法可以访问数据。如列的数据类型是map<string,int>，列某一行的值为{"xiao song":18,"xiaoxiao song":19}，那么可以通过 字段名['xiao song']获取第一个元素对应的值	MAP<primitive_type, data_type>
arrays	数组是一组具有相同类型和名称的变量的集合。这些变量称为数组的元素，每个数组元素都有一个编号，编号从零开始。如数组值为["bingbing","lili"]，那么第2个元素可以通过字段名[1]进行引用。	ARRAY<data_type>

3.2 复杂类型使用范例

  （1）创建本地测试文件test.txt

songsong,bingbing_lili,xiao song:18_xiaoxiao song:19,hui long guan_beijing
yangyang,caicai_susu,xiao yang:18_xiaoxiao yang:19,chao yang_beijing
cz,bingbing_lili,xiao song:18_xiaoxiao song:19,hui long guan_beijing
zx,caicai_susu,xiao yang:18_xiaoxiao yang:19,chao yang_beijing
zmy,bingbing_lili,xiao song:18_xiaoxiao song:19,hui long guan_beijing
tom,caicai_susu,xiao yang:18_xiaoxiao yang:19,chao yang_beijing
mike,bingbing_lili,xiao song:18_xiaoxiao song:19,hui long guan_beijing
jack,caicai_susu,xiao yang:18_xiaoxiao yang:19,chao yang_beijing

  （2）创建测试表test

create table test(
name string,
friends array<string>,
children map<string, int>,
address struct<street:string, city:string>
)
row format delimited fields terminated by ','
collection items terminated by '_'
map keys terminated by ':'
lines terminated by '\n';

字段解释：

row format delimited fields terminated by ','  -- 列分隔符
collection items terminated by '_'  	--MAP STRUCT 和 ARRAY 的分隔符(数据分割符号)
map keys terminated by ':'			-- MAP中的key与value的分隔符
lines terminated by '\n';				-- 行分隔符

  （3）导入文本数据到测试表

load data local inpath '/home/hdfs/test.txt' into table test;

  （4）访问三种集合列里的数据，（ARRAY，MAP，STRUCT的访问方式）

select friends[1],children['xiao song'],address.city from test;

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