Impala having 子句
The Having Impala 中的子句使你能够指定过滤哪些组结果出现在最终结果中的条件。
一般来说, Having 子句与 group by 子句;它将条件放在由 GROUP BY 子句创建的组上。
语法
以下是语法 Having clause.
select * from table_name ORDER BY col_name [ASC|DESC] [NULLS FIRST|NULLS LAST]
例子
假设我们有一个名为 顾客 在数据库中 my_db 其内容如下:
[quickstart.cloudera:21000] > select * from customers; Query: select * from customers +----+----------+-----+-------------+--------+ | id | name | age | address | salary | +----+----------+-----+-------------+--------+ | 1 | Ramesh | 32 | Ahmedabad | 20000 | | 2 | Khilan | 25 | Delhi | 15000 | | 3 | kaushik | 23 | Kota | 30000 | | 4 | Chaitali | 25 | Mumbai | 35000 | | 5 | Hardik | 27 | Bhopal | 40000 | | 6 | Komal | 22 | MP | 32000 | | 7 | ram | 25 | chennai | 23000 | | 8 | rahim | 22 | vizag | 31000 | | 9 | robert | 23 | banglore | 28000 | +----+----------+-----+-----------+--------+ Fetched 9 row(s) in 0.51s
下面是一个使用示例 Having Impala 中的子句:
[quickstart.cloudera:21000] > select max(salary) from customers group by age having max(salary) > 20000;
此查询最初按年龄对表进行分组,并选择每个组的最高薪水并显示那些大于 20000 的薪水,如下所示。
20000 +-------------+ | max(salary) | +-------------+ | 30000 | | 35000 | | 40000 | | 32000 | +-------------+ Fetched 4 row(s) in 1.30s