您可以使用Impala的 Union 子句合并两个查询的结果.
语法
以下是Impala中 Union 子句的语法.
query1 union query2;
示例
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 | | 9 | robert | 23 | banglore | 28000 | | 2 | Khilan | 25 | Delhi | 15000 | | 4 | Chaitali | 25 | Mumbai | 35000 | | 7 | ram | 25 | chennai | 23000 | | 6 | Komal | 22 | MP | 32000 | | 8 | ram | 22 | vizag | 31000 | | 5 | Hardik | 27 | Bhopal | 40000 | | 3 | kaushik | 23 | Kota | 30000 | +----+----------+-----+-----------+--------+ Fetched 9 row(s) in 0.59s
以同样的方式，假设我们有另一个名为 employee 的表及其内容如下 :
[quickstart.cloudera:21000] > select * from employee; Query: select * from employee +----+---------+-----+---------+--------+ | id | name | age | address | salary | +----+---------+-----+---------+--------+ | 3 | mahesh | 54 | Chennai | 55000 | | 2 | ramesh | 44 | Chennai | 50000 | | 4 | Rupesh | 64 | Delhi | 60000 | | 1 | subhash | 34 | Delhi | 40000 | +----+---------+-----+---------+--------+ Fetched 4 row(s) in 0.59s
以下是Impala中 union 子句的示例.在这个例子中，我们按照id的顺序排列两个表中的记录，并使用两个单独的查询将它们的数量限制为3，并使用 UNION 子句加入这些查询.
[quickstart.cloudera:21000] > select * from customers order by id limit 3 union select * from employee order by id limit 3;
执行时，上面的查询给出以下输出.
Query: select * from customers order by id limit 3 union select * from employee order by id limit 3 +----+---------+-----+-----------+--------+ | id | name | age | address | salary | +----+---------+-----+-----------+--------+ | 2 | Khilan | 25 | Delhi | 15000 || 3 | mahesh | 54 | Chennai | 55000 | | 1 | subhash | 34 | Delhi | 40000 | | 2 | ramesh | 44 | Chennai | 50000 | | 3 | kaushik | 23 | Kota | 30000 | | 1 | Ramesh | 32 | Ahmedabad | 20000 | +----+---------+-----+-----------+--------+ Fetched 6 row(s) in 3.11s
中获取6行