在带有附加列的配置单元中创建表

Question

I am new to Hive . I want to create the table in hive with the same columns as that of existing table plus some additional columns. I Know we can use something like this.

CREATE TABLE new_table_name
AS
SELECT *
FROM old_table_name

This will create the table with same columns as that of old_table_name.

But How do I specify additional columns in new_table_name ?

Answer 1

Here is how you can achieve it:

Old table:

hive> describe departments;
OK
department_id           int                     from deserializer   
department_name         string                  from deserializer   

Create table:

create table ctas as 
select department_id, department_name, 
cast(null as int) as col_null 
from departments;

Displaying Structure of new table:

hive> describe ctas;
OK
department_id           int                                         
department_name         string                                      
col_null                int                                         
Time taken: 0.106 seconds, Fetched: 3 row(s)

Results from new table:

hive> select * from ctas;
OK
2       Fitness         NULL
3       Footwear        NULL
4       Apparel         NULL
5       Golf            NULL
6       Outdoors        NULL
7       Fan Shop        NULL
8       TESTING         NULL
8000    TESTING         NULL
9000    testing export  NULL

Answer 2

简单的方法是发出ALTER TABLE命令以在上述CREATE语句之后添加更多（附加）列。

Answer 3

first create a new table like the first one and after that alter this new table and add the columns that you want.

CREATE TABLE new_table LIKE old_table;
ALTER TABLE new_table ADD COLUMNS (newCol1 int,newCol2 int);

if you wish to avoid data copy, make your table external

I wish that it helps you :)