RE: java code help...

Yes, that is a good point.  The AS qualifier will always work because the
JDBC driver's do not figure out the underlying columns being used in a
query,
they ask the database for the column names of the result table.  The AS
clause names a column in the Result table so it will always work.

There is nothing really preventing us from supporting qualified names
either.  Writing the code that would enable users to provide qualified
names would
not be too hard, but the performance overhead could be significant.

Richard D. Dettinger
AS/400 Java Data Access Team

Democracy's enemies have always underestimated the courage of the American
people.
It was true at Concord Bridge.  It was true at Pearl Harbor.  And it was
true today.

         Rochester Post-Bulletin
         Tuesday September 11, 2001


"David Morris" <David.Morris@plumcreek.com>@midrange.com on 11/20/2001
02:04:24 PM

Please respond to java400-l@midrange.com

Sent by:  java400-l-admin@midrange.com


To:   <java400-l@midrange.com>
cc:
Subject:  RE: java code help...



Richard,

One workaround is to use as. The following should work:

select a.field as afield, b.field as bfield from a join b...

Then specify afield and bfield. I have found the JDBC driver can vary
widely
in this area depending on who wrote it. For example, Oracle will let
you use
a qualified name with their OCI driver. Their thin driver will fail.
Both work with
ordinal references. All work with as or ordinal reference.

David Morris

> -----Original Message-----
> From:   Richard Dettinger [SMTP:cujo@us.ibm.com]
> Sent:   Friday, November 16, 2001 4:49 AM
> To:     java400-l@midrange.com
> Subject:     RE: java code help...
>
>
> You can't qualify column names.  Sorry its just not allowed.  The
> specification states that if a column name exists multiple times in
a
> ResultSet that the column name applies to the first entry.
>
> You could write your SQL statement to give the columns unique names.
> That's the only work around available.
>
> BTW:  Your app will perform better if you use the column indexes
instead
> of
> the column names.  Part of why using names instead of column indexes
is so
> expensive is because you have to do a linear search of the names of
the
> columns in the ResultSet for just this reason.  If your ResultSet has
100
> rows and you are fetching the 100th row with a column name, you could
be
> spending an order of magnitude more time in the driver figuring out
what
> the column index is over actually doing the work of getting the
data.
>
> Sorry, dude... I'm a JDBC driver writer... I have to say those types
of
> things to the application programmers.  :-)
>
> Richard D. Dettinger
> AS/400 Java Data Access Team
>
> Democracy's enemies have always underestimated the courage of the
American
> people.
> It was true at Concord Bridge.  It was true at Pearl Harbor.  And it
was
> true today.
>
>          Rochester Post-Bulletin
>          Tuesday September 11, 2001

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