How can we put comments in a column of existing MySQL table?

It can be done by using ‘COMMENT’ keyword while modifying the column with ALTER TABLE command. For example if we want to add comment in column ‘id’ of table ‘testing’ then following query will do it

mysql> ALTER TABLE testing MODIFY id INT COMMENT 'id of employees';
Query OK, 0 rows affected (0.07 sec)
Records: 0 Duplicates: 0 Warnings: 0

With following query it can be checked in the comment field of a column.

mysql> Show full columns from testing\G
*************************** 1. row ***************************
     Field: id
      Type: int(11)
 Collation: NULL
      Null: NO
       Key: PRI
   Default: 0
     Extra:
Privileges: select,insert,update,references
   Comment: id of employees
*************************** 2. row ***************************
     Field: Name
      Type: varchar(20)
 Collation: latin1_swedish_ci
      Null: YES
       Key:
   Default: NULL
     Extra:
Privileges: select,insert,update,references
   Comment:
2 rows in set (0.05 sec)