Hive--DQL操作

• 查看函数

show functions;
desc functions extended +;

• 关系运算符

  • 大小比较

  select 1>1;
  select 1=1;
  select 1>=1;
  

  • 空值判断

  select 'asd' is null;
  select 'asd' is not null;
  

  • 模糊查询

  select 'itcast' like 'it____'; _代表匹配一个字符
  select 'itcast' like 'it%'; _代表匹配任意个数字符
  

  • 正则查询

  select 'itcast' rlike 'it.';
  select 'itcast' regexp 'it.';
  

• 算数运算符

  • 加减乘除

  select 1+1;
  select 1/2;
  select 1/0;
  

  • 取整取余

  select 3 div 2;
  select 4 % 2;
  

  • 位运算

  0 0000 
  1 0001
  2 0010
  3 0011
  4 0100  
  5 0101
  6 0110
  select 4 & 6; 0100 * 0110     0100
  select 4 | 6  0100 | 0110  只要有一个位数是1 该位置上的数据就是1
  

• 逻辑运算符

  • 与或非

  select 1>1 and 1=1;  and 所有条件成立
  select 1>1 or 1=1;  or 一个条件成则返回true
  select  !1>1; 取反
  

  • 在范围内

  select 1 in (2,3);
  select 1 not in  (2,3);
  

• 字符串函数

-- 字符串长度函数
select length('asd');
-- 字符串反转函数
select reverse('asd');
-- 字符串连接函数
select concat('asd','zxc');
-- 分隔符字符串连接函数
select concat_ws('-','asd','zxc','aaa')
-- 字符串截取函数
select substr('itcast',2,2); -- 第一个截取字符的位置 第二个截取字符的个数
select substr('itcast',-2)
-- 字符串转大写函数
select upper('asd');
select lower('ASD');
-- 去空格函数
select trim(' aaa ');
select ltrim('  aaaa   ');
select rtrim('  aaaa   ');
-- 正则表达式替换函数
select regexp_replace('asd123','(\w+)d','aaa')
-- URL解析函数
select parse_url('http://www.baidu.com','HOST');
-- 割字符串函数
select split('asd,aaa',',')

• 时间日期函数

-- 获取当前日期
select `current_date`();
-- 获取当前时间戳
select `current_timestamp`();
-- UNIX时间戳转日期函数
select from_unixtime(1634528834);
-- 获取当前UNIX时间戳函数
select unix_timestamp();
-- 日期转UNIX时间戳函数
select unix_timestamp('2021-10-10 10:10:10');
-- 抽取日期函数
select to_date('2021-10-10 10:10:10');
-- 日期转年函数
select year('2021-10-10 10:10:10');
-- 日期比较函数
select datediff('2021-10-10 10:10:10','2021-10-12 10:10:10');
-- 日期增加函数
select date_add('2021-10-10 10:10:10',5);
select date_sub('2021-10-10 10:10:10',5);

• 数学函数

-- 取整函数
select round(3.1415);
-- 指定精度取整函数
select round(3.1415，2);
-- 向下取整函数
select `floor`(-1.1);
-- 向上取整函数
select ceil(1.1);
-- 进制转换函数
select conv()
-- 取随机数函数
select round(rand(3)*100);
-- 绝对值函数
select abs(-10)

• 集合函数

-- 集合元素数
select size(`array`('a','n','b'));
-- 取map集合keys函数
select map_keys(`map`('name','python','age',19));
-- 取map集合values函数
select map_values(`map`('name','python','age',19));
-- 判断数组是否包含指定元素
select array_contains(`array`(1,2,3),4);
select 1 in (1,2,3);
-- 数组排序函数
select sort_array(`array`(1,5,3,2));
select sort_array(`array`('g','a','f','c'));

• 条件函数

-- if条件判断
-- 空判断函数
-- 非空判断函数
-- 空值转换函数
-- 非空查找函数
select coalesce(null,null,2);
-- 条件转换函数

• 类型转换

select cast('12' as int);

• 数据脱敏

select mask('asd123ZXC');
select mask('asd123ZXC','*','@','#');
-- 对前n个进行脱敏替换
select mask_first_n('asd123',3);
select mask_last_n('itcastpython',3);
-- 除了前n个字符，其余进行掩码处理
select mask_show_first_n('asdzxc',2);
select mask_show_last_n('qwertyu',2);
-- 返回字符串的hash编码。xxxxxxxxxx select mask('asd123ZXC');select mask('asd123ZXC','*','@','#');--对前n个进行脱敏替换select mask_first_n('asd123',3);select mask_last_n('itcastpython',3);--除了前n个字符，其余进行掩码处理select mask_show_first_n('asdzxc',2);select mask_show_last_n('qwertyu',2);--返回字符串的hash编码。-- 脱敏--对前n个进行脱敏替换--除了前n个字符，其余进行掩码处理--返回字符串的hash编码。

• 其他

-- 反射函数
select reflect("java.lang.Math","max",11,22);
-- 取哈希值函数
-- SHA-1加密
-- MD5加密

• UDF 普通函数 输入一行输出一行
• UDAF 聚合函数 输入多行输出一行
• UDTF 输入一行输出多行

• explode（UDTF）

  • NBA总冠军球队

  create table the_nba_championship(
      team_name string,
      champion_year array
  ) row format delimited
  fields terminated by ','
  collection items terminated by '|';
  
  -- 使用explode函数对champion_year进行拆分
  
  
  

• lateral View

• 行列转换 concat

  列比较

  select count(case when gender='男' then id end) as '男'，count(case when gender='女' then id end) as '女' from students
  
  

  男	女
  30	40

  行比较

  select gender,count(id) as count from student group by gender
  
  

  gender	count
  男	30
  女	40

  • 行转列

  create table row2col2(
     col1 string,
     col2 string,
     col3 int
  )row format delimited fields terminated by 't';
  
  

  • 列转行

  create table col2row2(
     col1 string,
     col2 string,
     col3 string
  )row format delimited fields terminated by 't';
  
  

• json数据处理

  • 单个字段

  create table tb_json_test1 (
    json string
  );
  
  get_json_object(json,'$.deviceType')
  
  

  • 多个字段

  create table tb_json_test2 (
     device string,
     deviceType string,
     signal double,
     `time` string
   )
  ROW FORMAT SERDE 'org.apache.hive.hcatalog.data.JsonSerDe'
  STORED AS TEXTFILE;
  
   json_tuple(json,'device','deviceType')
  
  

  • serder

  create table tb_json_test2 (
     device string,
     deviceType string,
     signal double,
     `time` string
   )
  ROW FORMAT SERDE 'org.apache.hive.hcatalog.data.JsonSerDe'
  STORED AS TEXTFILE;
  
  

  -- 拓展--xml数据处理
  desc function extended xpath;
  SELECt xpath('b1b2b3c1c2', 'a/b/text()')
  
  

聚合函数、分析函数、排序函数 over(partition by 字段1… order by 字段1… rows 范围)

• 建表

---建表并且加载数据
create table website_pv_info(
   cookieid string,
   createtime string,   --day
   pv int
) row format delimited
fields terminated by ',';

create table website_url_info (
    cookieid string,
    createtime string,  --访问时间
    url string       --访问页面
) row format delimited
fields terminated by ','

• 求出每个用户总pv数sum+group by普通常规聚合操作

select cookieid,sum(pv) from website_pv_info group by cookieid;

• 求出网站总的pv数 所有用户所有访问加起来

• 求出每个用户总pv数

select cookieid,sum(pv) over(partition by cookieid) from website_pv_info;

• 求出每个用户截止到当天，累积的总pv数

-- 求出每个用户截止到当天，累积的总pv数  between unbounded preceding and current row 等价  unbounded preceding
-- order by 默认有一个计算范围 unbounded preceding
select cookieid,sum(pv) over(partition by cookieid order by createtime rows between unbounded preceding and current row ) from website_pv_info;
select cookieid,sum(pv) over(partition by cookieid order by createtime rows unbounded preceding) from website_pv_info;
select cookieid,sum(pv) over(partition by cookieid order by createtime ) from website_pv_info;

• 自定义窗口范围

unbounded preceding

• 找出每个用户访问pv最多的Top3重复并列的不考虑

-- 排序  rank 遇到重复会生成不连续的序号  dense_rank连续序号 row_number生成行号
select *,rank() over (partition by cookieid order by pv desc ) as rank_num from website_pv_info;
select *,dense_rank()  over (partition by cookieid order by pv desc ) as rank_num from website_pv_info;
select *,row_number()  over (partition by cookieid order by pv desc ) as rank_num from website_pv_info;
select *,ntile(3)  over (partition by cookieid order by pv desc ) as rank_num from website_pv_info;


with tb1 as ( select *,dense_rank()  over (partition by cookieid order by pv desc ) as rank_num from website_pv_info )
from tb1
select *
 where rank_num <= 3;

• 统计每个用户pv数最多的前3分之1天

with tb1 as (select *,ntile(3)  over (partition by cookieid order by pv desc ) as rank_num from website_pv_info)
from tb1
select *
 where rank_num = 1;

• 分析函数

select *,lag(pv)  over (partition by cookieid order by pv desc ) as rank_num from website_pv_info;
-- 向下取值
select *,lead(pv)  over (partition by cookieid order by pv desc ) as rank_num from website_pv_info;
-- 取第一个值
select *,first_value(pv)  over (partition by cookieid order by pv desc ) as rank_num from website_pv_info;
-- 去最后一个值 注意取值范围 因为orderby 所用取值范围需要增加向下的范围
select *,last_value(pv)  over (partition by cookieid order by pv desc rows between unbounded preceding and unbounded following) as rank_num from website_pv_info;


select sum(pv) sum(sum(pv)) over() from website_pv_info

• 压缩算法
• map压缩

1）开启hive中间传输数据压缩功能
set hive.exec.compress.intermediate=true;
2）开启mapreduce中map输出压缩功能
set mapreduce.map.output.compress=true;
3）设置mapreduce中map输出数据的压缩方式
Set mapreduce.map.output.compress.codec= org.apache.hadoop.io.compress.SnappyCodec;

• reduce压缩

1）开启hive最终输出数据压缩功能
set hive.exec.compress.output=true;
2）开启mapreduce最终输出数据压缩
set mapreduce.output.fileoutputformat.compress=true;
3）设置mapreduce最终数据输出压缩方式
set mapreduce.output.fileoutputformat.compress.codec = org.apache.hadoop.io.compress.SnappyCodec;
4）设置mapreduce最终数据输出压缩为块压缩
set mapreduce.output.fileoutputformat.compress.type=BLOCK;

• 行存储和列存储
• TextFILE
• ORC
• PAROUET
• 格式对比

TEXTfile

create table log_text (
track_time string,
url string,
session_id string,
referer string,
ip string,
end_user_id string,
city_id string
)ROW FORMAT DELIMITED FIELDS TERMINATED BY 't'
STORED AS TEXTFILE ;

orc

create table log_orc(
track_time string,
url string,
session_id string,
referer string,
ip string,
end_user_id string,
city_id string
)
ROW FORMAT DELIMITED FIELDS TERMINATED BY 't'
STORED AS orc ;

PARQUET

create table log_parquet(
track_time string,
url string,
session_id string,
referer string,
ip string,
end_user_id string,
city_id string
)
ROW FORMAT DELIMITED FIELDS TERMINATED BY 't'
STORED AS PARQUET ;	

• 查询速度对比

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-7ywnkF6o-1634628186284)(D:/Hadoop%E5%9F%BA%E7%A1%80/day09-Hive/day09-hive.assets/image-20211018155402681.png)]