Impala - 按条款排序

---

Impala ORDER BY子句用于根据一列或多列以升序或降序对数据进行排序。有些数据库默认按照升序对查询结果进行排序。

句法

以下是 ORDER BY 子句的语法。

select * from table_name ORDER BY col_name [ASC|DESC] [NULLS FIRST|NULLS LAST]

您可以分别使用关键字ASC或DESC以升序或降序排列表中的数据。

同样的，如果我们使用NULLS FIRST，表中所有的空值都会排列在最上面的行；如果我们使用 NULLS LAST，则包含空值的行将排列在最后。

例子

假设数据库my_db中有一个名为customer的表，其内容如下 -

[quickstart.cloudera:21000] > select * from customers;
Query: select * from customers 
+----+----------+-----+-----------+--------+ 
| id | name     | age | address   | salary | 
+----+----------+-----+-----------+--------+ 
| 3  | kaushik  | 23  | Kota      | 30000  | 
| 1  | Ramesh   |  32 | Ahmedabad | 20000  | 
| 2  | Khilan   | 25  | Delhi     | 15000  | 
| 6  | Komal    | 22  | MP        | 32000  | 
| 4  | Chaitali | 25  | Mumbai    | 35000  | 
| 5  | Hardik   | 27  | Bhopal    | 40000  | 
+----+----------+-----+-----------+--------+ 
Fetched 6 row(s) in 0.51s

以下是使用order by子句按ID升序排列客户表中数据的示例。

[quickstart.cloudera:21000] > Select * from customers ORDER BY id asc;

执行时，上述查询会产生以下输出。

Query: select * from customers ORDER BY id asc 
+----+----------+-----+-----------+--------+ 
| 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  | 
+----+----------+-----+-----------+--------+ 
Fetched 6 row(s) in 0.56s

同样，您可以使用order by子句将customers表的数据按降序排列，如下所示。

[quickstart.cloudera:21000] > Select * from customers ORDER BY id desc;

执行时，上述查询会产生以下输出。

Query: select * from customers ORDER BY id desc 
+----+----------+-----+-----------+--------+ 
| id | name     | age | address   | salary | 
+----+----------+-----+-----------+--------+ 
| 6  | Komal    | 22  | MP        | 32000  | 
| 5  | Hardik   | 27  | Bhopal    | 40000  | 
| 4  | Chaitali | 25  | Mumbai    | 35000  | 
| 3  | kaushik  | 23  | Kota      | 30000  | 
| 2  | Khilan   | 25  | Delhi     | 15000  |
| 1  | Ramesh   | 32  | Ahmedabad | 20000  | 
+----+----------+-----+-----------+--------+ 
Fetched 6 row(s) in 0.54s