DML

Load

LOAD DATA [LOCAL] INPATH 'filepath' [OVERWRITE] INTO TABLE tablename [PARTITION (partcol1=val1, partcol2=val2 ...)]

create table dept(
deptno int,
dname string,
location string
) row format delimited fields terminated by '\t';


LOAD DATA LOCAL INPATH '/home/hadoop/data/dept.txt' OVERWRITE INTO TABLE dept;

Overwrite 会删除原数据（覆盖），不加的话会add数据到table（添加）；

 

Insert

INSERT OVERWRITE [LOCAL] DIRECTORY directory1

  [ROW FORMAT row_format] [STORED AS file_format] (Note: Only available starting with Hive 0.11.0)

  SELECT ... FROM ...

INSERT OVERWRITE LOCAL DIRECTORY '/home/hadoop/data/d6/emptmp'
row format delimited fields terminated by ','
SELECT empno,ename FROM emp;


create table xxx as SELECT empno,ename FROM emp;

 

 

Hive里面的SQL

跟mysql一样的：

select ename, sal, 
case 
when sal > 1 and sal <=1000 then 'lower'
when sal > 1000 and sal <=2000 then 'middle'
when sal > 2000 and sal <=3000 then 'high'
else 'highest' end
from emp;

 

内置函数

upper lower

date
timestamp

 desc function extended abs;   查看内置函数的具体信息

分割：

拆开：

有时候须要转义字符

 

 

hive的wordcount全过程：

 

行转列

select word,count(1) as c
from
(select explode(split(sentence," ")) as word from hive_wc) t
group by word
order by c desc;

 

 

1) null 0 "" ''的区别

null是空值，比如空指针

0就是int值

""是空字符串

“ ”表示有一个空格的字符串

2) 求每个部门、工作岗位的最高薪资

 select deptno,job,max(sal) from emp group by deptno,job;

3) desc function extended abs; 中出现的案例是怎么来的呢

UDF函数里面有个@Description里面定义的

https://blog.csdn.net/HG_Harvey/article/details/77688735

4) 求每个月月底