【hive】hive的简单使用

在hive配好了之后：

hive的启动：输入"hive"就能启动了。

1，数据的显示

show databases;  --------能够显示当前的hive拥有的数据库；

use database_name;----------使用这个数据库；

show tables;--------能够展示当前数据库中拥有的数据表；

show tables in database_name;---------显示数据库下的数据表名；

describe/desc [extended/formatted]  database_name.table_name; ---------显示数据表的字段信息；[]中的选项可以显示详细以及更详细的信息。

 

2,join

jion操作是将两个及以上的表连接起来，根据不同的情况join分成：join,left outer join,right outer join,full out join。

以如下两张表为基础：

customers：

+----+----------+-----+-----------+----------+ 
| ID | NAME     | AGE | ADDRESS   | SALARY   | 
+----+----------+-----+-----------+----------+ 
| 1  | Ramesh   | 32  | Ahmedabad | 2000.00  |  
| 2  | Khilan   | 25  | Delhi     | 1500.00  |  
| 3  | kaushik  | 23  | Kota      | 2000.00  | 
| 4  | Chaitali | 25  | Mumbai    | 6500.00  | 
| 5  | Hardik   | 27  | Bhopal    | 8500.00  | 
| 6  | Komal    | 22  | MP        | 4500.00  | 
| 7  | Muffy    | 24  | Indore    | 10000.00 | 
+----+----------+-----+-----------+----------+

orders：

+-----+---------------------+-------------+--------+ 
|OID  | DATE                | CUSTOMER_ID | AMOUNT | 
+-----+---------------------+-------------+--------+ 
| 102 | 2009-10-08 00:00:00 |           3 | 3000   | 
| 100 | 2009-10-08 00:00:00 |           3 | 1500   | 
| 101 | 2009-11-20 00:00:00 |           2 | 1560   | 
| 103 | 2008-05-20 00:00:00 |           4 | 2060   | 
+-----+---------------------+-------------+--------+

两张表通过customers.id 和 orders.customer_id来连接，下面讨论不同join方式得到的结果。

1，join,就是内连接，如果只输出满足条件的数据。

SELECT c.ID, c.NAME, c.AGE, o.AMOUNT 
 FROM CUSTOMERS c JOIN ORDERS o  ON (c.ID = o.CUSTOMER_ID);

得到的结果如下：

+----+----------+-----+--------+ 
| ID | NAME     | AGE | AMOUNT | 
+----+----------+-----+--------+ 
| 3  | kaushik  | 23  | 3000   | 
| 3  | kaushik  | 23  | 1500   | 
| 2  | Khilan   | 25  | 1560   | 
| 4  | Chaitali | 25  | 2060   | 
+----+----------+-----+--------+

2，left outer join,左连接，连接的左表要全部都输出，不满足条件的左表数据用NULL代替：

 SELECT c.ID, c.NAME, o.AMOUNT, o.DATE 
 FROM CUSTOMERS c LEFT OUTER JOIN ORDERS o 
 ON (c.ID = o.CUSTOMER_ID);

结果如下所示：

+----+----------+--------+---------------------+ 
| ID | NAME     | AMOUNT | DATE                | 
+----+----------+--------+---------------------+ 
| 1  | Ramesh   | NULL   | NULL                | 
| 2  | Khilan   | 1560   | 2009-11-20 00:00:00 | 
| 3  | kaushik  | 3000   | 2009-10-08 00:00:00 | 
| 3  | kaushik  | 1500   | 2009-10-08 00:00:00 | 
| 4  | Chaitali | 2060   | 2008-05-20 00:00:00 | 
| 5  | Hardik   | NULL   | NULL                | 
| 6  | Komal    | NULL   | NULL                | 
| 7  | Muffy    | NULL   | NULL                | 
+----+----------+--------+---------------------+

3，right outer join,右连接，连接的右表要全部都输出，不满足条件的右表数据用NULL代替：

该部分的与“left outer join,左连接”相似，略过。

4，full outer join,全连接，需要连接的两张表的数据全部都输出。其本质上是先对数据进行左连接，然后再对数据进行右连接，再将结果连接起来。

SELECT c.ID, c.NAME, o.AMOUNT, o.DATE 
FROM CUSTOMERS c 
FULL OUTER JOIN ORDERS o ON (c.ID = o.CUSTOMER_ID);

结果为：

+------+----------+--------+---------------------+ 
| ID   | NAME     | AMOUNT | DATE                | 
+------+----------+--------+---------------------+ 
| 1    | Ramesh   | NULL   | NULL                | 
| 2    | Khilan   | 1560   | 2009-11-20 00:00:00 | 
| 3    | kaushik  | 3000   | 2009-10-08 00:00:00 | 
| 3    | kaushik  | 1500   | 2009-10-08 00:00:00 | 
| 4    | Chaitali | 2060   | 2008-05-20 00:00:00 | 
| 5    | Hardik   | NULL   | NULL                | 
| 6    | Komal    | NULL   | NULL                |
| 7    | Muffy    | NULL   | NULL                |  
| 3    | kaushik  | 3000   | 2009-10-08 00:00:00 | 
| 3    | kaushik  | 1500   | 2009-10-08 00:00:00 | 
| 2    | Khilan   | 1560   | 2009-11-20 00:00:00 | 
| 4    | Chaitali | 2060   | 2008-05-20 00:00:00 | 
+------+----------+--------+---------------------+