> Thanks, Stefan,
> But that only works if both tables have the same field name, doesn't it? If I
> use select FileKey from dl_files left join dl_merges using (FileID) where
> FileID is null MySQL returns
> Unknown column 'articles.dl_files.FileID' in 'on clause'.
> Correct me if I'm wrong, but wouldn't I have to modify the column name in
> one of the tables in order for that to work? Or is there a syntax in the
> join lexicon that I can use to alias one of the column names within the
> query? I can't modify the existing table structure(s).
> Apologies if I'm being dense.
> Make a good day ...
> ... barn
Well, that's what happens when you don't include relevant information, such as
your table definitions, in your question.
No, you don't need to modify your tables. You just need to use the join syntax
that fits your situation. USING works when the join column has the same name in
each table. Otherwise, you need to use ON. Hence, you need something like
LEFT JOIN dl_merges ON dl_files.ID = dl_merges.FileID
WHERE FileID IS NULL;
See the manual for details <http://dev.mysql.com/doc/refman/4.1/en/join.html>.