I want to select all contacts records for which the 'prospective customer.supplier' is not set to certain values.

I want to select all contacts records for which the 'prospective customer.supplier' is not set to certain values.

Apologies I'm new to Zoho and coming from a SQL background I'm trying to figure out how or rather if I can do the same in Zoho.
I have a Contacts table from which I wish to do a Mailing
and I have a 'Prospective Customer' table which has a field called Supplier.
For some mail shots I wish to restrict the contacts I send emails to by the value in the $(Prospects Customer.Supplier) field.  I might for example not wish to send certain emails to Prospective Customers that already use our supplier.

In sql it would look a little like 
   select * from Contacts 
   where account_id 
   not in (select account_id from Prospects Customer
        where supplier = "example")