From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | JT Kirkpatrick <jt-kirkpatrick(at)mpsllc(dot)com> |
Cc: | "'pgsql-sql(at)hub(dot)org'" <pgsql-sql(at)hub(dot)org> |
Subject: | Re: [SQL] finding the most recent records |
Date: | 1999-04-30 16:10:08 |
Message-ID: | 28978.925488608@sss.pgh.pa.us |
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Lists: | pgsql-sql |
JT Kirkpatrick <jt-kirkpatrick(at)mpsllc(dot)com> writes:
> "field1 datetime not null default text 'now'". you'll only run into a
> problem if more than one record is inserted AT THE EXACT SAME SECOND
> -- but postgres will just put the same timestamp in there (don't
> define the field as unique).
Actually, I think "now" means "the time at the start of the current
transaction", so that you'll get the same timestamp applied to all
records inserted within a transaction. This is good for some things;
for example, you can insert related records into several different
tables and expect them to have the same timestamp, even though the
operation may take more than a second to complete. But it does mean
that you can't expect a timestamp to serve as a unique ID. (Use a
SERIAL column for that, instead...)
regards, tom lane
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