Selecting records that have not been previously selected

[basildon]

Hi

I have a database of company details which I supply to my customers (held on MySQL).

Sometimes customers want a top up of records matching their specification but, oviously, they don't want records that they have previously been sent.

Currently I extract the records using SQL and then use a Perl script to remove the previously sent records.

I'd like to know whether there is a quicker SQL based solution to this problem as this process is often repeated and I think could be dramatically improved.

Many Thanks for any help

 

[Zodiak99]

The first thing that came to my mind was adding at least one extra field to your DB table(s) that stores a flag 'already_dloaded' with 0/1 as possible values.
On a second thought this is a rather suboptimal solution since you will problably have more than one customer downloading records. In any case seems you need another table that holds information like customer_id, already_dloaded and record_id (maybe as a foreign key). Somthing along these lines.
But I am not a database professional, so you might/will hopefully get better ideas from other users here ;-)

Regards,
Zodiak