查询语法
SELECT [ALL | DISTINCT] select_expr, select_expr, ...
FROM table_reference
[WHERE where_condition]
[GROUP BY col_list]
[ORDER BY col_list]
[CLUSTER BY col_list
| [DISTRIBUTE BY col_list] [SORT BY col_list]
]
[LIMIT [offset,] rows]
基本查询
select * from emp; select t.empno,t.ename,t.deptno from emp t;
limit
select * from emp limit 5;
区间查询between and
select * from emp e where e.sal between t.sal=10 and t.sal =1500;空查询is null
select t.empno,t.ename,t.deptno from emp t where t.deptno is null不空查询is not null
select t.empno,t.ename,t.deptno from emp t where t.deptno is not null集合查询in
select t.empno,t.ename,t.deptno from emp t where t.ename in ('lizh','forrest');不在集合范围内not in
select t.empno,t.ename,t.deptno from emp t where t.ename not in ('lizh','forrest');
函数查询
最高工资max
select max(sal) from emp e;最低工资min
select min(sal) from emp e;总人数count
select count(*) from emp e;公司月总支出sum
select sum(sal) from emp e;平均工资avg
select avg(sal) from emp e;
高级查询
分组group by
每个部门的平均工资
select e.deptno,avg(e.sal) from emp e group by e.deptno;
having
where:是针对单条记录进行筛选。
having是针对分组数据进行筛选
求每个部门平均工资大于2000的数据
'select e.deptno,avg(e.sal) avgsal from emp e group by e.deptno having avgsal>2000;'
join
两个表进行连接,例如有两个表m n ,m表中的一条记录和n表中的一条记录组成一条记录。
join on :等值连接
bin/hive -e 'select e.empno,e.ename, d.deptno,d.dname from emp e join dept d on e.deptno = d.deptno;'
left join:左连接
说明:左连接表示以join左边数据为主,若join右边的数据不存在则补空。
bin/hive -e 'select e.empno,e.ename, d.deptno,d.dname from emp e left join dept d on e.deptno = d.deptno;'
right join
说明:右连接表示以join左边数据为主,若join左边的数据不存在则补空。
bin/hive -e 'select e.empno,e.ename, d.deptno,d.dname from emp e right join dept d on e.deptno = d.deptno;'