How can I change column comments in existing Hive table without including new column name and type?

Question

I want to change the column comments on an existing hive table using hive 0.13. This works:

create table test (mycolumn int); alter table test change mycolumn mycolumn int comment 'hello';

But I can't find a way to do this without repeating the name of the column and the type, both of which are irrelevant to the change. For example:

alter table test change mycolumn comment 'hello'; leads to an error.

If this was for one column it would not be a big deal but I want to do this for large numbers of columns in tables that were not commented. I know this could be done with a script that simply copies the column name and its type but would be nice to know if there were something simpler. Thanks

Answer 1

You can do this using ALTER command.

CREATE TABLE my_table
(id INT COMMENT 'id comment',
name STRING comment 'name comment');

-- change column comment as below.
ALTER TABLE my_table CHANGE id id INT COMMENT 'another comment';
-- see changed column
DESC EXTENDED my_table;

Answer 2

ALTER TABLE test_change CHANGE a1 a1 INT COMMENT 'this is column a1';