复合类型构建操作
1. Map类型构建: map
语法: map (key1, value1, key2, value2, …)
说明:根据输入的key和value对构建map类型
举例:
hive> Create table lxw_test as select map('100','tom','200','mary') as t from lxw_dual;
hive> describe lxw_test;
t map<string,string>
hive> select t from lxw_test;
{"100":"tom","200":"mary"}
2. Struct类型构建: struct
语法: struct(val1, val2, val3, …)
说明:根据输入的参数构建结构体struct类型
举例:
hive> create table lxw_test as select struct('tom','mary','tim') as t from lxw_dual;
hive> describe lxw_test;
t struct<col1:string,col2:string,col3:string>
hive> select t from lxw_test;
{"col1":"tom","col2":"mary","col3":"tim"}
3. array类型构建: array
语法: array(val1, val2, …)
说明:根据输入的参数构建数组array类型
举例:
hive> create table lxw_test as select array("tom","mary","tim") as t from lxw_dual;
hive> describe lxw_test;
t array<string>
hive> select t from lxw_test;
["tom","mary","tim"]
十、复杂类型访问操作
1. array类型访问: A[n]
语法: A[n]
操作类型: A为array类型,n为int类型
说明:返回数组A中的第n个变量值。数组的起始下标为0。比如,A是个值为['foo', 'bar']的数组类型,那么A[0]将返回'foo',而A[1]将返回'bar'
举例:
hive> create table lxw_test as select array("tom","mary","tim") as t from lxw_dual;
hive> select t[0],t[1],t[2] from lxw_test;
tom mary tim
2. map类型访问: M[key]
语法: M[key]
操作类型: M为map类型,key为map中的key值
说明:返回map类型M中,key值为指定值的value值。比如,M是值为{'f' -> 'foo', 'b' -> 'bar', 'all' -> 'foobar'}的map类型,那么M['all']将会返回'foobar'
举例:
hive> Create table lxw_test as select map('100','tom','200','mary') as t from lxw_dual;
hive> select t['200'],t['100'] from lxw_test;
mary tom
3. struct类型访问: S.x
语法: S.x
操作类型: S为struct类型
说明:返回结构体S中的x字段。比如,对于结构体struct foobar {int foo, int bar},foobar.foo返回结构体中的foo字段
举例:
hive> create table lxw_test as select struct('tom','mary','tim') as t from lxw_dual;
hive> describe lxw_test;
t struct<col1:string,col2:string,col3:string>
hive> select t.col1,t.col3 from lxw_test;
tom tim
十一、复杂类型长度统计函数
1. Map类型长度函数: size(Map<K.V>)
语法: size(Map<K.V>)
返回值: int
说明: 返回map类型的长度
举例:
hive> select size(map('100','tom','101','mary')) from lxw_dual;
2
2. array类型长度函数: size(Array<T>)
语法: size(Array<T>)
返回值: int
说明: 返回array类型的长度
举例:
hive> select size(array('100','101','102','103')) from lxw_dual;
4
3. 类型转换函数
类型转换函数: cast
语法: cast(expr as <type>)
返回值: Expected "=" to follow "type"
说明: 返回array类型的长度
举例:
hive> select cast(1 as bigint) from lxw_dual;
1
4. 其他
cast 函数:
类型转换函数,cast(kbcount as int);
case when:
条件判断,case when kbcount is not null and cast(kbcount as int) >= cast(patch_count as int) then '1' else '0' end as isinstalled ;
语法:方法1
(
case sex
when '1' then '男'
when '2' then '女'
else '未知'
end
) as 性别
方法2
case
when sex='1' then '男'
when sex='2' then '女'
else '未知'
end as 性别
from_unixtime:将unix时间戳转化为制定格式的时间
from_unixtime(unix_timestamp(),'yyyy-MM-dd HH:mm:ss') as xdsp_last_update_time
lcase() :将字段的值转换为小写
lcase(t.info_iot_name)
hive collect_set: 可以得到分组后,其他合并元素的制定位置的值作为去重后的值。
表明:user
id , name, url
1 shao www
1 shao1 www1
2 zhi www
2 zhi1 www.ee
2 zhi2 www.2323
3 qi www.eere
3 qi2 www.urr
想要得到:
id , name, url
1 shao www
2 zhi www
3 qi www.eere
sql实现:方法1
select id ,collect_set(name)[0],collect_set(url)[0]
from user
group by id;
方法2:
select id ,max(name),max(url)
from user
group by id;
字符串max:字符串按照字母A-Z,越往后值越大
汉字按照全拼字母排,第一个字母相同则看第二个
concat() : 将两个或者多个字符串连接起来,如果有任何一个参数为null,则返回值为null
a.os_version like concat('%','2012r2','%')
concat_ws(): 以第一个参数为分隔符,将其他参数连起来
concat_ws('.',os_version_main,os_version_sp,os_version_bit,os_version_sub)