Re: Advice - indexing on varchar fields where only last x characters known

Hi,
PostgreSQL does have the ability to index on expressions. Will that help?
http://www.postgresql.org/docs/9.1/static/indexes-expressional.html
I think mentioning the version of PostgreSQL you are using, sample
queries/plans etc will help.
Jayadevan

On Thu, Oct 17, 2013 at 4:50 PM, Gary Stainburn <
gary(dot)stainburn(at)ringways(dot)co(dot)uk> wrote:

> I have a problem with a field that appears on a number of my tables.
>
> The field is the Vehicle Identification Number. Every vehicle has one and
> it
> uniquely identifies that vehicle.
>
> Traditionally this was a 11 character string but a number of years ago was
> extended to 17 characters by adding a 6 character prefix.
>
>
> The problem that I have is that these VIN numbers are provided by a number
> of
> data systems including manufacturer feeds, logistics companies as well as
> internal systems. Some use the full 17 character string while others only
> use
> the last 11.
>
> On top of this, my users are used to only having to type the last 6
> characters
> for speed and usability reasons.
>
> However, it means that every time I'm trying to connect various tables up
> using foreign keys or doing searches I have to make allowences for this
> which
> means I'm using things like substring, like, regex etc. all of which are
> very
> slow.
>
> Can anyone suggest a better / more efficient way of handling these.
>
> Gary
>
>
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