hive  select查詢語句

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SELECT [ALL | DISTINCT] select_expr, select_expr, ...

FROM table_reference
[WHERE where_condition]
[GROUP BY col_list]
[LIMIT number]


eg:
select empno, count from db_hive_emp limit 5 ;
limit:
從查詢分析的結果集中顯示多少條資料。


>>>>>>>>
全表查詢、指定欄位查詢
use db_hive_0927 ;
select * from emp ;   -- 不跑mr任務
select empno, ename, deptno from emp ;   --執行mr任務


>>>>>>>>
= />= / <= /between and /limit
select empno, ename, deptno from emp where empno >= 7782 ;
select * from emp limit 5 ;
查詢emp中工資在800 到 1500 之間的人
select ename, sal from emp where sal between 800 and 1500 ;


>>>>>>>>>>
(not) in / is (not) null
select ename, sal, comm from emp where comm is null ;
select ename, sal, comm from emp where comm is not null ;


>>>>>>>>>
max/min/count/sum/avg 
select count(*) from emp ;
select count(1) from emp ;
select max(sal) max_sal from emp ;
select avg(sal) avg_sal from emp ;


>>>>>>>>>
group by / having
select deptno ,count(1) cnt from emp group by deptno ;


select deptno ,avg(sal) cnt from emp group by deptno ;


having 是對分組結果進行篩選的
select deptno ,avg(sal) avg_sal from emp group by deptno having avg_sal > 2000 ;