Impala GROUP BY 子句与SELECT语句配合使用,将相同的数据排列成组.
以下是GROUP BY子句的语法.
select data from table_name Group BY col_name;
假设我们在数据库中有一个名为 customers 的表 my_db 及其内容如下 :
[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 | +----+----------+-----+-----------+--------+ Fetched 6 row(s) in 0.51s
您可以使用GROUP BY查询获得每个客户的工资总额,如下所示.
[quickstart.cloudera:21000] > Select name, sum(salary) from customers Group BY name;
执行时,上面的查询给出以下输出.
Query: select name, sum(salary) from customers Group BY name +----------+-------------+ | name | sum(salary) | +----------+-------------+ | Ramesh | 20000 | | Komal | 32000 | | Hardik | 40000 | | Khilan | 15000 | | Chaitali | 35000 | | kaushik | 30000 | +----------+-------------+ Fetched 6 row(s) in 1.75s