Ugly problem with USING vs ON in JOIN

[Joe Pluta <joepluta@xxxxxxxxxxxxxxxxx>]

Here's a real beauty.  Try this with any file:

with t1 as (select key1, data1 from myfile)
  select t1.* from t1 join myfile using (key1)

Then try this:

with t1 as (select key1, data1 from myfile)
  select t1.* from t1 join myfile on t1.key1 = myfile.key1


myfile is any file with a single unique key field.  key1 is that key 
field.  data1 is any other field in the file.  Actually, it doesn't HAVE 
to be that way; you can use any two fields.  But if you don't use a 
unique field you may end up with a REALLY big result set.

The first select will return only data1 in the result set, while the 
second will return both key1 and data1.  I'm one behind on DB2 group 
PTFs, but this is a pretty big one and it just bit me badly.

Please note that this is a completely stripped down query and I realize 
that it effectively does "select key1, data1 from myfile".  The actual 
query is much more involved.  But this reproduces the problem in the 
fewest steps.

Now I have to start looking for USING in all my queries.

Joe