Обсуждение: serial type vs. sequences

I was wondering if there was a reliable method to get the last id
inserted into a serial column in a table.  I believe previous
recommendations given were to use a sequence, have your app get the
nextval for the sequence and then use that in the insert.  I was
wondering if things had changed or if that is still the recommended
method.

--
Suchandra Thapa <s-thapa-11@alumni.uchicago.edu>

On Wed, Nov 12, 2003 at 14:59:33 -0600,
  Suchandra Thapa <s-thapa-11@alumni.uchicago.edu> wrote:
> I was wondering if there was a reliable method to get the last id
> inserted into a serial column in a table.  I believe previous
> recommendations given were to use a sequence, have your app get the
> nextval for the sequence and then use that in the insert.  I was
> wondering if things had changed or if that is still the recommended
> method.

It is probably a little better to use currval rather than remembering
what nextval returned in your application.

You are accurate.

Suchandra Thapa wrote:

>I was wondering if there was a reliable method to get the last id
>inserted into a serial column in a table.  I believe previous
>recommendations given were to use a sequence, have your app get the
>nextval for the sequence and then use that in the insert.  I was
>wondering if things had changed or if that is still the recommended
>method.
>
>
>

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Joshua D. Drake wrote:

> You are accurate.
>
> Suchandra Thapa wrote:
>
>>I was wondering if there was a reliable method to get the last id
>>inserted into a serial column in a table.  I believe previous
>>recommendations given were to use a sequence, have your app get the
>>nextval for the sequence and then use that in the insert.  I was
>>wondering if things had changed or if that is still the recommended
>>method.

If you don't need the value itself in your application, it is safe to
use currval('seqname') in queries following the use of
nextval('seqname'). currval() returns the last value assigned in your
session and is not affected by other concurrent transactions.


Jan

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