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.有些数据库默认按升序对查询结果进行排序.
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 按升序或降序排列表中的数据.
In同样，如果我们使用NULLS FIRST，表中的所有空值都排列在顶行;如果我们使用NULLS LAST，则包含空值的行将排在最后.
假设我们有一个名为的客户表在数据库 my_db 中，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
以下是在 customers 表格中安排数据的示例 id
[quickstart.cloudera:21000] > Select * from customers ORDER BY id asc;
执行时，上述查询产生以下输出.
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
以同样的方式，您可以安排 customers 表中的数据降序使用 order by 子句，如下所示.
[quickstart.cloudera:21000] > Select * from customers ORDER BY id desc;
执行时，上述查询产生以下输出.
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中获取6行
