From: | Chris Browne <cbbrowne(at)acm(dot)org> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: not so sequential sequences |
Date: | 2006-10-17 22:26:10 |
Message-ID: | 60irii7f5p.fsf@dba2.int.libertyrms.com |
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Thread: | |
Lists: | pgsql-general |
rhys(dot)stewart(at)gmail(dot)com ("Rhys Stewart") writes:
> Hi all, looking for a method to number a table sequentially, but the
> sequence only increments if the value in a certain column is
> different. as in
>
>
> seq | parish
> ------------------------
> 1 | Kingston
> 1 | Kingston
> 1 | Kingston
> 1 | Kingston
> 2 | Lucea
> 3 | Morant Bay
> 3 | Morant Bay
> 3 | Morant Bay
> 4 | Port Antonio
> 5 | Savannah-La-Mar
> 5 | Savannah-La-Mar
> 5 | Savannah-La-Mar
>
> so i guess i would order by a certain column and then the 'magic
> sequence' would be a column that only increments when the column
> changes.
The usual way to do this would be to separate out what clearly is a
dependant table; the seq and parish values could be associated with a
smaller table that increments any time you get a new parish.
The process of doing this sort of separation is called "normalization."
<http://en.wikipedia.org/wiki/Database_normalization>
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