Обсуждение: Serial / auto increment data type

On Wed, 2005-04-27 at 15:43, Typing80wpm@aol.com wrote:
> I am just beginning to teach myself Postgresql and Access.  I notice
> that PG has the "serial" type of field which increments
> automatically.   I notice that when I do external links in Access
> through ODBC, that Access wants a field or fields which will be
> unique.
>
> Here is my question.  Would I be wise to define each and ever table
> with a serial id, so that I may always be guaranteed something uniqe,
> to satisfy Access.   It seems to me like no harm can be done, since if
> you dont need the serial id, you dont need it, but it is always there
> if you do need it, and it is harder to add such a field down the line,
> after the fact.

Since 7.4 or 7.3 (I forget which) serial has NOT guaranteed uniqueness.
you have to add unique or primary key to the declaration like so:

create table foo (bar serial unique, otherfield int);

Or replace "unique" with "primary key"...

Yes, that is the way to do it.

I migrated several large Access DB to postgres and most of the tables that where done by the
non developers didn't have a primary key defined, so the easiest way was just to add a new field to every table and
makeit a serial. 

I believe you would have to do this even if you were using MS SQL server as the backend.

> Here is my question.  Would I be wise to define each and ever table with
> a serial id, so that I may always be guaranteed something uniqe, to
> satisfy Access.   It seems to me like no harm can be done, since if you
> dont need the serial id, you dont need it, but it is always there if you
> do need it, and it is harder to add such a field down the line, after
> the fact.
>
> Thanks!

--
Tony Caduto
AM Software Design
Home of PG Lightning Admin for Postgresql 8.x
http://www.amsoftwaredesign.com