[INNER JOINS, excluding records based on other tables]

Thanks for your help.  I had to use a subquery to get this to work but again, thanks for your help!

[INNER JOINS, excluding records based on other tables]

Hello,

I'm creating a photo gallery and for individual photos, you may "tag" one.  For example, when someone makes a stupid face in the photo, you may give the photo the "Funny" tag.  Each photo may have multiple tags (e.g. "Funny", "Stupid", "Idiot"). 

To let users add a tag to a photo, I give them a "<SELECT>" box to choose from a list of existing tags.  Obviously, if the photo already has the "Stupid" tag, I do not want tag showing up in the dropdown list.

I'm having problems coming up with a good MySQL statement to get the information.  The tables are as follows:

MEDIA
--------------
media_id
media_title
......

MEDIA TAG
--------------
media_id
tag_id
user_id

USERS
--------------
user_id
user_handle
....

Seeing as tags can be used on multiple photos, the JOIN seems to be pretty complicated.

I've tried a variation of the following with incorrect results:

SELECT * FROM dg_tags t
LEFT JOIN (dg_media_tags mt)
ON (t.tag_id = mt.tag_id AND mt.media_id != 6)
ORDER BY t.tag_title

What can I do to get the select box of "tags" that arent' in use for a specific photo?

Thank you!