We'll have to agree to disagree. Just because I add a "deserves_a_payrise"
column to an employee table, doesn't necessarily mean I want it to appear
everywhere automatically :-)
Cheers,
Kerry S
----- Original Message -----
From: Carl Reynolds <[EMAIL PROTECTED]>
To: Multiple recipients of list database <[EMAIL PROTECTED]>
Sent: Friday, October 15, 1999 12:27 PM
Subject: RE: [DUG-DB] Select * (was: (Informix) Where can I get sqlca.h?)
> >Kerry's executive summary: SELECT * is a bad thing, *especially* in
> >Informix-4GL -- less so in Delphi because you can use FieldByName.
>
> Yeah, well who uses I4GL anymore anyway... :P
>
> Our database is fairly fluid in that clients are always thinking up new
> and interesting columns that everyone wants to see. Judicious use of
> FieldByName has enabled us to avoid any problems of the type you mention
> - tables can have their columns reordered or removed without any
> hassles; just got to remember never to use positional references (and as
> an aside, I just read Aaron's reply where he advocates building arrays
> of field offsets - sounds like a good alternative).
>
> There are some advantages to using select * in Delphi. Much of our
> software is build specific, but some pieces aren't, specifically
> producing an ad-hoc report of a table (including automatic lookups,
> because our databases contain data dictionary information like joins,
> table descriptions and so forth), exporting the data to a file, and
> copy-and-pasting from a DBGrid into (for example) Excel. Users can
> filter their data and choose which columns they want to see, and any new
> columns are immediately available, to display, sort by, copy, export and
> filter on. There are a lot of tables displayed using these screens - if
> we nailed down the format of the database on every build, we would have
> a fair bit of work to identify and fix all the code every time the
> database changes (although SQA robot helps). We already have enough
> work changing code when things change. It's a constant struggle because
> you can't afford to miss anything, but you have to keep productivity
> high...
>
> Another use for select * would be if users were allowed to create their
> own custom columns on tables, but realistically nobody lets this happen
> - there are other and better ways to do it.
>
> Perhaps I should get back to work now... :\
>
> Cheers,
>
> Carl Reynolds Ph: +64-9-4154790
> CJN Technologies Ltd. Fax: +64-9-4154791
> [EMAIL PROTECTED] DDI: +64-9-4154795
> PO Box 302-278, North Harbour, Auckland, New Zealand
> 12 Piermark Drive, North Harbour Estate, Auckland, NZ
> Visit our website at http://www.cjntech.co.nz/
>
> > -----Original Message-----
> > From: Kerry Sainsbury [SMTP:[EMAIL PROTECTED]]
> > Sent: Friday, October 15, 1999 11:19 AM
> > To: Multiple recipients of list database
> > Subject: Re: [DUG-DB] (Informix) Where can I get sqlca.h?
> >
> > Carl Reynolds <[EMAIL PROTECTED]> said
> >
> > > (Having said that, I think the best reason to use "SELECT * FROM
> > table"
> > > is if you know the table definition _is_ likely to change. That way
> > you
> > > keep your rewriting of code to a minimum).
> >
> > Ever tried to install a system that runs over a WAN? Performance
> > improves
> > quite a lot if you only SELECT the columns your application is using.
> >
> > Ever tried accessing the columns from a SELECT * statement, on a table
> > which
> > has had the order of the columns rearranged? (Which is totally fine by
> > me,
> > BTW)
> >
> > Ever had SELECT * code go bang when an obsolete column is removed from
> > a
> > table, eg:
> >
> > Old customer table:
> > name varchar(50);
> > telex varchar(15);
> > phone varchar(15);
> >
> > 'Fixed' customer table:
> > name varchar(50);
> > phone varchar(15);
> >
> > When your application attempts to access 'phone' based on it's
> > position
> > (fields[3]) things get ugly.
> >
> > Also, SELECT customer.*, order.* FROM customer, order ... causes all
> > sorts
> > of grief if columns get added or removed and positional references to
> > fields
> > are used.
> >
> > Kerry's executive summary: SELECT * is a bad thing, *especially* in
> > Informix-4GL -- less so in Delphi because you can use FieldByName.
> >
> > > Now sit down and breathe deeply... :) :)
> >
> > Calm blue Ocean.
> > Calm blue Ocean.
> >
> > ----------------------------------------------------------------------
> > -----
> > New Zealand Delphi Users group - Database List -
> > [EMAIL PROTECTED]
> > Website: http://www.delphi.org.nz
>
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Website: http://www.delphi.org.nz
