Re: only best matches with ilike or regex matching

On 1/17/07, Ron Arts <ron(dot)arts(at)neonova(dot)nl> wrote:
>
> this is probably an SQL question instead of PostgreSQL but here it goes.
>
> I have a table containing phone destinations and pricing as follows:
>
> prefix | cost | timeframe | provider
> ----------------------------------------
> ^31 | 0.02 | 1 | 1
> ^31 | 0.01 | 2 | 1
> ^31653 | 0.14 | 1 | 1
> ^31653 | 0.12 | 2 | 1
> ^31 | 0.03 | 1 | 2
> ^31 | 0.02 | 2 | 2
> ^31653 | 0.15 | 1 | 2
> ^31653 | 0.13 | 2 | 2
>
> where timeframe=2 means weekends.
>
> For a given phonenumber I need to get the list of providers with the
> cheapest one first. Suppose the target phonenumber is 31653445566,
> and timeframe is 2:
>
> prefix | cost | timeframe | provider
> ----------------------------------------
> ^31653 | 0.12 | 2 | 1
> ^31653 | 0.13 | 2 | 2
>
> But I cannot find a query to get this result. I only want
> the ^31653 rows, and not the ^31 rows, but these both match
> a 'where'31653445566' ~ prefix' clause. Using distinct does not
> work as well.
>

This is close...

# select * from phonerates where '^316534455665' like prefix || '%' and
timeframe = 2 order by length(prefix) desc, cost asc limit 1;
prefix | cost | timeframe | provider
--------+------+-----------+----------
^31653 | 0.12 | 2 | 1

If you want exactly as you indicated above, then...

select *
from phonerates
where timeframe = 2
and prefix = (select prefix
from phonerates
where '^316534455665' like prefix || '%'
order by length(prefix) desc
limit 1)
order by cost;

prefix | cost | timeframe | provider
--------+------+-----------+----------
^31653 | 0.12 | 2 | 1
^31653 | 0.13 | 2 | 2

--
Chad
http://www.postgresqlforums.com/