Please help with outer join....

I have the following situation...

I have 4 tables that I want to do a "select" on:

FILES:       FILEID,FILENAME,OUTBYUSERID, FILEDETAILS: FILEID,CUSTOMERID
USERS:       USERID,USERNAME
CUSTOMERS:   CUSTOMERID,CUSTOMERNAME OUTBYUSERID is a foreign key into the USER (USERID) table, but if no user has the file "checked-out", it is NULL.

How should this select statement read? I know if OUTBYUSERID was always a foreign key into USERS that I could use:

SELECT * FROM CUSTOMERS,FILES,FILEDETAILS,USERS

   WHERE CUSTOMERS.CUSTOMERID = FILEDETAILS.CUSTOMERID AND
         FILEDETAILS.FILEID = FILES.FIEID AND
         FILES.OUTBYUSERID = USERS.USERID AND
         FILES.FILEID = 3;

And that does work as long as OUTBYUSERID isn't NULL, but when OUTBYUSERID is NULL, no matches are made.

I guess what I am asking is what is the proper syntax for OUTER JOINS with multiple tables. If you could just change the above statement so that it works correctly...that would be OUTSTANDING! :)

Thanks,
Shayne

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