HIV语法

• 1、创建数据库
  create database hive_db;

  显示数据库中表

  show tables;

  切换数据库

  use hive_db;

  显示数据库中

  show databases;

  显示某表结构，两种方式 1：表结构 2：表结构和分区数据位置等

  desc 表名;
  show create table 表名

• 2、创建表脚本
  2.1 内部表-直接建表
  create table IF NOT EXISTS orders
  (
  order_id string comment "订单编号",
  user_id string comment "用户ID",
  order_number string comment "下单顺序",
  order_dow string comment "下单日期周一到周日",
  order_hour_of_day string comment "下单时间",
  days_since_prior_order string comment "距离上一次购物时间"
  )
  ROW FORMAT DELIMITED FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n'
  STORED AS TEXTFILE;

  create table IF NOT EXISTS order_product(
   order_id string comment "订单编号",
   product_id string comment "物品ID",
   add_to_cart_order string comment "加入购物车时间",
   reordered string comment "是否复购"
  )
  ROW FORMAT DELIMITED FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n'
  STORED AS TEXTFILE;
  

  2.1 查询建表
  #场景：建立一个临时表，或者一个中间表
  create table movies_tem as select * from movies limit 100;
  2.2 like 建表
  CREATE TABLE IF NOT EXISTS default.weblog_20150923
  LIKE default.weblog ;

• 3、导入数据
  3.1 本地导入
  load data local inpath ‘/user/root/custom.csv’ overwrite into table 表明
  #用overwrite 加载本地数据到hive数据仓库
  #local:加上local指本地的数据路径，也就是在linux系统下的文件路径
  #不加local：指文件在hdfs下的路径，文件上传到hdfs后的路径

• 4、collect_list和collect_set
  它们都是将分组中的某列转为一个数组返回，不同的是collect_list不去重而collect_set去重。
  https://www.cnblogs.com/cc11001100/p/9043946.html

• 5、split分割和数组转行
  select split("I Love you", " ")
  select explode(split("I Love you", " "));

• 6、row_number()、rank()、dense_rank()三个函数区别

• 7、时间窗口
  row_number() over()
  sum() over()

  从最早的时间距你当前的时间

  select *, sum(result) over (partition by user_name order by create_time) as result_sum
  from user_match_temp

  从你当前时间到当前时间的前三条数据，不包括本条数据

  select *, avg(result) over (partition by user_name order by create_time rows between 3 preceding and current row) as recenty_wins
  from user_match_temp

• 8、case when 条件表达式 then 表达式为true返回值 else 表达式为false返回值 end
  select uid,iid,score,case when score<=1 then '0-1' when score>1 and score<=3 then '1-3' when score>3 then '3-5' else '-1' end as
  score_rank from movies limit 30;

• 9、if(条件表达式,表达式为true返回值,表达式为false返回值)

• 10、自定义函数（UDF\UDAF\UDTF）

• 11、concat 拼接
  select concat("{",'aaa',"}");

• 12、regexp_replace #正在表达式
  select regexp_replace("'course')}", "^\W+|\W+$","")

• 13、 针对json格式进行解析处理并转换成多行处理

a:shangdong,b:beijing,c:shanghai	1,2,3	[{"source":"7fresh","monthSales":4900,"userCount":1900,"score":"9.9"},{"source":"jdmart","monthSales":7900,"userCount":2900,"score":"5.9"},{"source":"yam","monthSales":54900,"userCount":12900,"score":"4.9"}]
a:tianjing,b:beijing,c:shanghai	3,4,5	[{"source":"7fresh","monthSales":4900,"userCount":1900,"score":"9.9"},{"source":"jdmart","monthSales":7900,"userCount":2900,"score":"5.9"},{"source":"yam","monthSales":54900,"userCount":12900,"score":"4.9"}]

#去掉开头和结尾的[{、}]
select regexp_replace(sale_info,'\\[\\{|\\}\\]','') from explode_test

"source":"7fresh","monthSales":4900,"userCount":1900,"score":"9.9"},{"source":"jdmart","monthSales":7900,"userCount":2900,"score":"5.9"},{"source":"yam","monthSales":54900,"userCount":12900,"score":"4.9"
"source":"7fresh","monthSales":4900,"userCount":1900,"score":"9.9"},{"source":"jdmart","monthSales":7900,"userCount":2900,"score":"5.9"},{"source":"yam","monthSales":54900,"userCount":12900,"score":"4.9"

# 拆分并转成多行
select explode(split(regexp_replace(sale_info,'\\[\\{|\\}\\]',''),"\\},\\{")) from explode_test
~~~显示结果
"source":"7fresh","monthSales":4900,"userCount":1900,"score":"9.9"
"source":"jdmart","monthSales":7900,"userCount":2900,"score":"5.9"
"source":"yam","monthSales":54900,"userCount":12900,"score":"4.9"
"source":"7fresh","monthSales":4900,"userCount":1900,"score":"9.9"
"source":"jdmart","monthSales":7900,"userCount":2900,"score":"5.9"
"source":"yam","monthSales":54900,"userCount":12900,"score":"4.9"

通过get_json_object函数转换成json并获取json中属性

select
get_json_object(concat("{",t.infos,"}"),"$.source"),
get_json_object(concat("{",t.infos,"}"),"$.monthSales"),
get_json_object(concat("{",t.infos,"}"),"$.score")
from
(
select explode(split(regexp_replace(sale_info,'\[\{|\}\]',''),"\},\{")) as infos from explode_test
)t

7fresh	4900	9.9
jdmart	7900	5.9
yam	54900	4.9
7fresh	4900	9.9
jdmart	7900	5.9
yam	54900	4.9

扩展，如果显示area，如何处理，可以通过udtf即lateral view进行实现

select
area,
get_json_object(concat("{",infos,"}"),"$.source"),
get_json_object(concat("{",infos,"}"),"$.monthSales"),
get_json_object(concat("{",infos,"}"),"$.score")
from explode_test lateral view explode(split(regexp_replace(sale_info,'\[\{|\}\]',''),"\},\{")) g as infos

针对hive一些配置说明
1、当select * from xxx，不能显示列名的时候，可以到hive-site.xml里面添加
   <property>
       <name>hive.cli.print.current.db</name>
       <value>true</value>
       </property>
   <property>
       <name>hive.cli.print.header</name>
       <value>true</value>
   </property>
或者进入hive之后 
   – set hive.cli.print.current.db=true;
   – set hive.cli.print.header=true;