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Impala教程

Impala Having

Impala 中的 Having 子句使您能够指定条件来过滤哪些组结果出现在最终结果中。
通常, Having 子句与 group by 子句一起使用;它将条件放在由 GROUP BY 子句创建的组上。

语法

以下是 Having子句的语法。
select * from table_name ORDER BY col_name [ASC|DESC] [NULLS FIRST|NULLS LAST]

示例

假设我们在数据库 my_db中有一个名为 customers的表,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
以下是在 Impala 中使用 Having 子句的示例-
[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工资并显示那些大于 20000 的工资,如下所示。
20000 
+-------------+ 
| max(salary) |
+-------------+ 
| 30000       |
| 35000       | 
| 40000       | 
| 32000       | 
+-------------+ 
Fetched 4 row(s) in 1.30s
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