Mysql:how to change table comment after created already?

Question

How to do it with mysql-cli? table comment means for example foo below:

create table t (c1 int) comment='foo';

Answer 1

you can use mysql> alter table t comment='f1';
mysql> commit;

Answer 2

As far as I know it is impossible to achieve that with an alter. Instead, I would do the following:

Step 1: Find out the definition of the table

Run

show create table t;

and save the result somewhere (clipboard or file, whatever)

Step 2: Create a similar table

Run

create table t_temp ...

(where... is the continuation of the command, do not take that literally, see Step 1 )

Step 3: Copy your data to the temp table

Run

insert into t_temp(...)
select ...
from t;

where ... represents the column list. Again, do not take this literally.

Step 4: Drop the current table

Run

drop table t;

Step 5: Rename the temp table

alter table t_temp rename t;

Final note

I strongly recommend that you back up your database regularly and specifically before you do such large changes to avoid irreparable data-loss.

Answer 3

Check if this answers your question. stackoverflow.com/questions/2162420/alter-mysql-table-to-add-comments-on-columns

thanks. @JoseLora