From: Rob <[EMAIL PROTECTED]>
> Hi, I'm working on a script that has to find if there is a customer
> number in one table that's not in the other. My first thought was to
> write all customer numbers out to a file then sort them and go through
> the first file one line at a time while going completly through the
> other file each time. But from what I've seen with Postgres so far I
> would bet that I could do the same thing with a select statement.
> Would this be possible? Would I need to use a join for something like
> this?
I've never worked with Postgres, but maybe something like this would
work:
select customer_no
from Table1
where not exists (select * from Table2 where Table1.customer_no =
Table2.customer_no)
or maybe
select customer_no
from Table1
where Table1.customer_no not in (select customer_no from Table2)
If you for whatever reason did try to search through the numbers
yourself I would recomend
1) ask the Postgres to sort the numbers, don't do it yourself
select customer_no from Table1 order by customer_no
2) instead of saving the numbers from the second table to a flat file
and searching the file completely each time keep them in a hash.
And if the hash would be too big, use DB_File or some similar module
to keep the hash on disk.
In either case this will be much much quicker.
Jenda
=========== [EMAIL PROTECTED] == http://Jenda.Krynicky.cz ==========
There is a reason for living. There must be. I've seen it somewhere.
It's just that in the mess on my table ... and in my brain
I can't find it.
--- me
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