Default values for all users in mysql table

In my app, I allow people to create additional rooms for inventory purposes. Let's say I have a table called "user_data." The d_key field is the data type for a lack of a better description. I have that just in case I introduce more custom fields for the user. Anyways, I want every user to have a room that's called None. This way any item that doesn't have a room assigned to it will default to "None."

What's the best way to introduce None into the table? Users won't be able to delete this default room, but they can edit/delete rooms they input into the DB table.

user_data table

+---------+-------------+------+-----+---------+----------------+
| Field   | Type        | Null | Key | Default | Extra          |
+---------+-------------+------+-----+---------+----------------+
| id      | int(11)     | NO   | PRI | NULL    | auto_increment |
| user_id | int(11)     | NO   |     | NULL    |                |
| d_key   | varchar(20) | NO   |     | NULL    |                |
| d_value | varchar(40) | NO   |     | NULL    |                |
+---------+-------------+------+-----+---------+----------------+

Sample data:

+----+--开发者_开发知识库-------+----------+--------------+
| id | user_id | d_key    | d_value      |
+----+---------+----------+--------------+
| 20 |       2 | location | bedroom      |
| 21 |       2 | location | living room  |
| 22 |       2 | location | attic        |
| 23 |       3 | location | kitchen      |
+----+---------+----------+--------------+

Add the row as part of your user creation process.

For existing users, loop over the users and ensure they have a "none" room; if they don't, insert one.