CFParam link to a table with no record

Question

Guys, I'm a newb feeling my way a long with CF, and have made
some good headway. Here's my challenge de jour:
I have a main table, `customers`. I have two other tables,
`products` and `customers_products`. The latter has four fields:
its own primary key, a customer_id, a product_id, and the
product_name.
For the sake of my question, I've loaded `customers_products`
with dummy data that relates perfectly with some `customer`s and
their `products`, using their respective keys. I can easily insert
new records to this table, `customer_products`, for any customer by
using an INSERT form, as long as there is already at least one
customer record in the `customer_product` table. But, if I attempt
to go to
add_product.cfm?customer_id= from that customer form for a
customer who has yet to have any products entered in
`customer_products`, I get the error, "Invalid data '' for
CFSQLTYPE CF_SQL_NUMERIC". This, I presume, due to the null value,
as the CRParam URL is the customer_id - and there is no customer_id
in that table, yet.
I want to be able to go from the customer record form to the
add_products.cfm form, specifically for that customer, even though
there are no current records for that customer in the
`customer_products` table.
I'd add code, but I have a feeling that this is not so much a
problem with code, but lack of knowledge of how to do a common
practice: add a new record to a table and applying the correct
customer key to the customer_id field.
If you know of a site or tutorial that I can use, that would
be great.
Thank you!

Answer 1

If your SQL query is looking at the URL for an ID in order to
query the table and it doesn't exist you'll get a query.recordcount
of 0. You can then use this to direct the user to another
page...like an add page or something. At the same time you could
also check the ID is right before querying the database (my syntax
may be a little incorrect as I am doing this from memory at 8am!)
e.g.
<cfif isDefined("url.customer_id") and
len(url.customer_id)>
<!---Do your query here.--->
<cfif my_query.recordcount eq 0>
<!--- the URL existed but the query returned 0 so let's
redirect them to the add page or something --->
<cflocation url="my_add_page.cfm" addtoken="no" />
<cfabort />
</cfif>
<cfelse>
<!---URL looks bad.--->
<p>Nothing was found because the URL looks
wrong.</p>
</cfif>