Impala - ORDER BY 子句

Impala 的ORDER BY子句用于根据一个或多个列对数据进行升序或降序排序。某些数据库默认按升序对查询结果进行排序。

语法

以下是 ORDER BY 子句的语法。

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

您可以使用关键字ASC或DESC分别将表中的数据排列为升序或降序。

同样，如果我们使用 NULLS FIRST，则表中的所有空值都排列在顶部行；如果我们使用 NULLS LAST，则包含空值的行列将排列在最后。

示例

假设我们在数据库my_db中有一个名为customers的表，其内容如下所示：

[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

以下是如何使用order by子句按id的升序排列customers表中的数据的示例。

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

执行上述查询后，将产生以下输出。

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，您可以使用如下所示的order by子句将customers表中的数据按降序排列。

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

执行上述查询后，将产生以下输出。

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