HIVE--常用hql语句

Hive 的启动方式：1、hive 命令行模式，直接输入/hive/bin/hive的执行程序，或者输入 hive - -service cli

2、hive web界面的启动方式，hive - -service hwi

3、hive 远程服务 (端口号10000) 启动方式，nohup hive - -service hiveserver & 
 创建表cite，并指定列的分隔符为“,”：create table cite(citing INT, cited INT) row format delimited    fields terminated by ‘,’;
创建表page_view，并指定分区字段为dt，同时把列的分隔符设置为“,”：

create table page_view (pid INT, url string) partitioned by (dt string) row format delimited  fields terminated by ‘,’;

创建表S_USER_ERROR，并指定分区字段为YEAR、MONTH和DAY，同时把列的分隔符设置为“,”，最后指定表的存储路径为/data/stg/s_user_error/：CREATE TABLE S_USER_ERROR

(

bar          INT,

foo          string

)

PARTITIONED BY (YEAR STRING,MONTH STRING,DAY STRING)

ROW FORMAT DELIMITED FIELDS TERMINATED BY ‘,’ STORED AS TEXTFILE LOCATION ‘/data/stg/s_user_error/’;
注意：如果不是外表部，drop table的时候会将HDFS上文件删除。
创建外部表：CREATE EXTERNAL TABLE lhttest (

id int,

name string

)

PARTITIONED BY (pt string)

ROW FORMAT DELIMITED

FIELDS TERMINATED BY ‘,’

STORED AS TEXTFILE

LOCATION ‘/data/stg/lhttest’;
注意：在删除外部表的时候，不会删除HDFS上的关联文件。

把一个本地系统中的文件加载到visiter表的2010-06-08分区下：

load data local inpath ‘/root/user/myHiveTestFile/02’ overwrite into table visiter PARTITION (dates=‘2010-06-08’);
查询cite表的前3行记录：select * from cite limit 3;

描述表pv的结构：Describe  pv;desc pv;
删除表：drop table lhttest;

把表page_view重命名为pv：Alter table   page_view   rename to pv;

给表pv添加一个名为IP的列：Alter table   pv  add columns (ip  string);

添加一个分区：Alter table pv add  partition (dt=‘2012-06-26’);
把已经存在的一个目录设置为表的一个分区：alter table pv  add partition (dt= ‘2012-06-27’)  location ‘/hive/warehouse/pv/2012-06-27’;
显示一个表的分区信息：show partitions  lhtstudent;
删除一个分区：Alter table pv drop partition (dt=‘2012-06-26’);

从lhtstudent的分区2012-06-26中查出数据，插入到studentnum的名为2012-06-26的分区中：

insert overwrite table studentnum partition (dt=‘2012-06-26’) select count(1) from lhtstudent where dt=‘2012-06-26’

取lhtstudent中字段name的前3个字符：

Select    substr(name,0,3)   as   subname   from lhtstudent;

对字段id进行去重操作：

Select  distinct(id)   from lhtstudent;

通过Join关联查询（相当于inner join）：select distinct i.id,i.name,s.score from lhtstudent i join studentscore s on i.id = s.stuid;
通过left outer join关联查询（相当于sql的left join）：select  i.id,i.name,s.score from lhtstudent i left outer join studentscore s on i.id = s.stuid;
通过right outer join关联查询（相当于sql的right join）：select  i.id,i.name,s.score from lhtstudent i right outer join studentscore s on i.id = s.stuid;
通过order by 进行排序：select * from lhtstudent order by id desc;
通过like进行模糊查询：select * from lhtstudent where name like ‘%liu%’;
通过group by 进行排序：select id from lhtstudent group by id;
通过case语句进行转换：select case dt when ‘2012-06-25’ then ‘今天’ when ‘2012-06-26’ then ‘明天’ end from lhtstudent;
select score , ( case when score >= 60 then ‘及格’  when score < 60 then ‘不及格’ end) from lhtstudent;
通过concat连接两个字符串：select concat(id,name) from lhtstudent;
upper()字符串转大写：select upper(name) from lhtstudent;
lower()字符串小写：select lower(name) from lhtstudent;
length()取到字符串长度：select name,length(name) from lhtstudent;
trim()去空格：select trim(name) from lhtstudent;
year(string date)返回年：select year(‘2012-07-11 12:30:50’) from lhttest;  //返回2012
month(string date) 返回月：select month(‘2012-07-11 12:30:50’) from lhttest;//返回7
day(string date) 返回日：select day(‘2012-07-11 12:30:50’) from lhttest;//返回11
dayofmonth(date)返回一个月中的第几天：select dayofmonth(‘2012-07-11 12:30:50’) from lhttest;//返回11
hour(string date) 返回小时：select hour(‘2012-07-11 12:30:50’) from lhttest;//返回12
minute(string date) 返回分钟：select minute(‘2012-07-11 12:30:50’) from lhttest;//返回30
second(string date) 返回秒：select  second(‘2012-07-11 12:30:50’) from lhttest;//返回50
weekofyear(string date) 返回一年中的第几周：select weekofyear(‘2012-07-11 12:30:50’) from lhttest;//返回28
datediff(string enddate, string startdate) 返回enddate和startdate的天数的差：select datediff(‘2012-07-11’,‘2012-07-09’) from lhttest;//返回2
select datediff(‘2012-07-11’,‘2012-07-12’) from lhttest;//返回-1
date_add(string startdate, int days) 加days天数到startdate:select date_add(‘2012-07-11’,1) from lhttest;//返回2012-07-12
date_sub(string startdate, int days)  从startdate减去days天：select date_sub(‘2012-07-11’,1) from lhttest;//返回2012-07-10
to_date(string timestamp) 返回日期字符串:select to_date(‘2012-07-12 10:30’) from lhttest; //返回2012-07-12
unix_timestamp() 获得当前时间戳:select  unix_timestamp()  from lhttest;//返回当前时间的秒数
from_unixtime(int unixtime) 将时间戳（unix epoch秒数）转换为日期时间字符串:select from_unixtime(1341910120) from lhttest;//返回2012-07-10 16:48:40
select from_unixtime(0) from lhttest;//返回1970-01-01 00:00:00