Need To Modify This SQL...

The following was not written by me but I need to modify it and I am definitely no expert in SQL. It returns a list of files that a user is allowed to access based on whether or not they belong to a specific user group and that group has been granted access to the file.

Here is the SQL as it is currently:

SELECT a.ID, a.Title, a.Description, a.FileName, a.DateCreated, a.DateModified, u.UserName, a.UserID, COUNT(ga.AnswerFileID) AS ShareCount

FROM
User AS u INNER JOIN

AnswerFile AS a LEFT OUTER JOIN

GroupAnswerFile AS ga LEFT OUTER JOIN

GroupUser AS gu
ON ga.GroupID = gu.GroupID ON a.ID = ga.AnswerFileID ON u.ID = a.UserID

GROUP BY a.ID, a.Title, a.Description, a.FileName, a.DateCreated, a.DateModified, a.UserID, u.UserName, gu.UserID

HAVING (gu.UserID = 2)

UNION

SELECT a.ID, a.Title, a.Description, a.FileName, a.DateCreated, a.DateModified, u.UserName, a.UserID, 0 AS ShareCount

FROM AnswerFile AS a INNER JOIN User AS u ON a.UserID = u.ID

WHERE (a.UserID = 2) AND (a.ID NOT IN SELECT AnswerFileID FROM GroupAnswerFile))

I need to modify this code to add an additional check. I have added a file that allows specific users to be granted access to files. It is called AnswerFileUser and contains AnswerFileID (the file) and UserID (the user that has been given access). I need the query to return as part of the results those files where a user has been given access regardless of their group or group access. I hope this all makes sense. Thanks for your help!

Oops - this is SQL 2005...