Обсуждение: Re: Primary Key with serial the solution?
How about if i do this inside a procedure:
SELECT setval('sequence',(SELECT max(id) FROM table)) INTO variable;
insert into table values(variable, ..., ...); ?
Will this be transactional? Cause, they say that setval is a command that its transactional. Using this way i
don´t will need to use a sequence anymore. Is that correct?
Thanks you all.
2008/3/31, x asasaxax <xanaruto@gmail.com>:
can anyone do a example for me.. an explain how it works?Thanks a lot
2008/3/29, Berend Tober <btober@ct.metrocast.net>:x asasaxax wrote:
> I have the following table create table product(cod serial, user_cod
> bigint, constraint product_fk Foreign Key(user_cod) references user(cod),
> constraint product_pk Primary Key(cod, user_cod));
>
> What i want to happend is that:
> user_cod cod
> 1 1
> 1 2
> 1 3
> 2 1
> 3 1
> 3 2
>
> Can serial do that? ...
No.
> ...what can i do to make this happen?
http://archives.postgresql.org/pgsql-general/2006-08/msg00744.php
x asasaxax wrote: > How about if i do this inside a procedure: > > SELECT setval('sequence',(SELECT max(id) FROM table)) INTO variable; > insert into table values(variable, ..., ...); ? > > Will this be transactional? Cause, they say that setval is a command > that its transactional. Using this way i > don´t will need to use a sequence anymore. Is that correct? If somebody else INSERTs a record between your first and second statements, it will get the first free value in the sequence so your INSERT will fail with a unique check voliation. Assuming there's a unique constraint involved, which I assume there is given your use of a sequence. Why do you want to do this? Sequences are designed so that you can just: INSERT INTO table VALUES ( nextval('sequence'), ..., ...) or set the DEFAULT on the generated value field such that it calls nextval('sequence') if the user just does: INSERT INTO table VALUES ( DEFAULT, ... , ... ) or uses a named-field INSERT and omits the sequence column entirely. Why not use them that way? Is there something you're trying to achieve that sequences aren't doing the job for - like, say, "gap-less" generated values? If that's the problem please search the archives as it's already been discussed to death even in the short time I've been a list member. -- Craig Ringer