Impala order by 子句
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。一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]
你可以使用关键字以升序或降序排列表格中的数据 ASC or DESC 分别。
同理,如果我们使用NULLS FIRST,表中的所有空值都排列在最上面几行;如果我们使用 NULLS LAST,则包含空值的行将排在最后。
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 | +----+----------+-----+-----------+--------+ | 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
以下是排列数据的示例 顾客 表,按其升序排列 id’s 使用 order by clause.
[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
同理,你可以整理数据 顾客 使用降序排列的表格 order by 子句如下图。
[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