Re: i have table

On 10/4/06 12:20 PM, "Aaron Bono" <postgresql(at)aranya(dot)com> wrote:

> On 10/4/06, Erik Jones <erik(at)myemma(dot)com> wrote:
>>
>> Aaron Bono wrote:
>>> On 10/4/06, *Erik Jones* <erik(at)myemma(dot)com <mailto:erik(at)myemma(dot)com>>
>>> wrote:
>>>
>>> There is one non-SQL related reason that I like to be able to order
>>> columns, at least the way they are displayed whenever the table is
>>> described: human comprehension. For example, I like to group all
>>> keys
>>> in a table before data, that includes primary as well as foreign
>>> keys.
>>> So, say I'm building on to an existing application and I need to do
>> an
>>> ALTER TABLE on an existing table to add a foreign key to an existing
>>> table. I'd like that key to be listed with the other keys, but
>>> presently that's not possible in a simple way and, to be honest, I
>>> usually just go without as the process you've described below is too
>>> prone to user (human) error when dealing with live, sensitive data
>> for
>>> me to want to mess with it.
>>>
>>>
>>> Ah, but it is possible... if you use views.
>>>
>>> I recommend you build views and query off them. Then you can control
>>> the order the columns will appear.
>> Which would be great if I didn't have (many) thousands of lines of code
>> that already use the tables. Besides, this is no where near a 'make or
>> break' thing. It's just a matter of aesthetic preference.

Ah, but it *is* a "make or break thing." I have seen more than one
application crash because some developer didn't understand that columns in a
relation (table) have no defined order.

This (along with its sister axiom that rows have no defined order) is one of
the most commonly misunderstood aspects of relational databases.

>
>
>
> So do it as needed and convert your application slowly.
>
> I just name my views as table_name_vw so all you have to do is modify your
> queries to hit the _vw instead of just the table. That shouldn't take much
> time to refactor.
>
> ==================================================================
> Aaron Bono
> Aranya Software Technologies, Inc.
> http://www.aranya.com
> http://codeelixir.com
> ==================================================================

--
Daryl
http://itsallsemantics.com