Hi!

>Hi Andrew,
>
>If you can explain your first idea more detailed, it would be great.

Nadya, it looks like you don't know RDBMS theory well ;) Sorry, just kidding. I will try to explaing it by easy way.

In RDBMS theory many-to-many relationship should be established by using separate additional table to preserve third normal form of database. For example:

Customer
Cust_id name address

Product
prod_id name description

Many-to-many relationship will be done using third table

CustProd
Cust_id Prod_id date_bought


As you see, this way allows also add some additional information. You way will look here like following:

Customer
Cust_id name address mapto='A8', 'BCD' etc.

Product
prod_id = 'A', '8', 'B' etc.

Do you see difference?

Anyway, seems you will not accept such database changes because you already have a lot of data, as you said. In addition, third notmal form for Many-to-many relationship is good for flexibility, but bad for queries. Your query in such case for 'AND' will look like following:

Select * from Customers
Where cust_id IN (select cp.cust_id from CustProd cp inner join products p
on p.prod_id = cp.prod_id where prod_id = 'A')
AND cust_id IN (select cp.cust_id from CustProd cp inner join products p
on p.prod_id = cp.prod_id where prod_id = '8')

Nice, heh? I don;t know about speed, however. Last query definitely will run more quickly on SQL server, but will be slower with VFP database through network because plenty of indexes for optimization.