Re: Tuple data

Поиск
Список
Период
Сортировка
От Emmanuel Charpentier,,,
Тема Re: Tuple data
Дата
Msg-id 3A3DC70D.7050703@bacbuc.dyndns.org
обсуждение исходный текст
Ответ на Re: Tuple data  (Hiroshi Inoue <Inoue@tpf.co.jp>)
Список pgsql-hackers
Hiroshi Inoue wrote :

[ ... ]

> Column order isn't essential in rdbms.

<Nitpicking>

A relation (a table) is a subset of the Cartesain cross-product of the 
definition domains of the attributes (columns). Cartesian product being 
a commutative operation, "order of columns" does not really exists. Period.

If you impose an order relationship, you *add* inforation to the 
structure. That may be OK, but you can't rely on relational algebra to 
guarantee your results. You'll have to manage it yourself. (And, yes, 
there is relevant algebra for this, too ...).

</Nitpicking>

> Isn't it well known that it's not preferable to use
> 'select *','insert' without column list etc.. in production
> applications ?

100% agreed. Such a notation is an abbreviation. Handy, but dangerous. 
IMHO, such checking can (should ?) be done by an algorithm checking for 
column *names* before sending the "insert" command.

A partial workaround : inserting in a view containing only the relevant 
columns, in a suitable (and known) order.

[ Back to lurking ... ]



В списке pgsql-hackers по дате отправления:

Предыдущее
От: vs
Дата:
Сообщение: LM devel GLIB2_2
Следующее
От: Thomas Lockhart
Дата:
Сообщение: Re: Re: Beos update