hive常用sql彙總

1.hive分組去重函數使用。

select  *,row_num() over(partition by id order by modifytime desc) rn from lyjtest  where rn=1;
 row_num() over函數對id做分區根據修改時間做降序，然後篩選出時間最新的一條（rn=1）的數據，達到去重的效果。

2.hive 寫入數據
insert into table table2 select * from table1; --查詢table1中的數據寫入table2;
insert overwrite table table2 select * from table1;--覆蓋寫入

3.where和having的區別

//where是先限定性條件再分組(對原始數據過濾,where不能過濾聚合函數)
hive> select count(*),age from table1 where id>18 group by age;

//having是先分組在限定條件(對每個組進行過濾,having後只能跟select中已有的列)
hive> select age,count(*) c from table1 group by age having c>2;

//where和having一起使用
select id,count(*) from table1 where id>18 group by id having count(*)>2;

4.hive只支持union all，不支持union
  union all 不去重
  select name,age from table1 where id<80
  union all
  select name,age from table2 where age>18;

5.查詢前五條數據
select * from table1 order by age desc limit 5; --查詢年齡最大的五條數據
select * from student limit 5;--隨機查詢五條數據

6.五種子句的嚴格順序

where → group by → having → order by → limit

7.distinct

//distinct關鍵字返回唯一不同的值(返回age和id均不相同的記錄)
hive> select distinct age,id from test;

8.複製表
create table test1_temp  like test1; --只複製表不包含數據
create  table test1 as select * from test2; --複製表複製數據到新表9.創建表

9.創建表

CREATE TABLE `lyjtest1`(     `id` double,   `name` string, `sex` string) 
COMMENT 'create table from sql'
ROW FORMAT SERDE  'org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe'  
WITH SERDEPROPERTIES (  'field.delim'='\t',  'line.delim'='\n', 'serialization.format'='\t')   
STORED AS INPUTFORMAT   'org.apache.hadoop.mapred.TextInputFormat'
OUTPUTFORMAT   'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'
LOCATION   'hdfs://ambari1:8020/warehouse/tablespace/managed/hive/ods_lyjtest.db/lyjtest1' ;