You can only revoke a privilege that you have granted. Even if another user has granted a privilege on an object that you own, you cannot revoke it.
You can revoke privileges selectively on a column, but the privilege must have been explicitly granted to the column. You cannot grant a privilege to an entire table and then revoke the privilege for a column in the table.
you want to revoke the GRANT option from a user or role, you have to take two separate actions. First you have to REVOKE the privilege itself, and then regrant the privilege without using the GRANT option.
To revoke the INSERT privilege on the COIN table that was granted in the previous
REVOKE INSERT ON COIN
Notice that you can grant ALL privileges for a table to a user and then selectively revoke individual privileges. The ALL keyword is simply a way of specifying all privileges with a single word, so the individual privileges can still be taken away.
The next lesson is the module wrap-up, which includes a quiz that will indicate what you have learned and discover topics that you might want to review in a more detailed manner.