Re: Curious SQL question

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Sat, 06 Jan 2007 13:43:27 GMT
Message-ID: <3INnh.41260$cz.607000_at_ursa-nb00s0.nbnet.nb.ca>

J M Davitt wrote:

> Neo wrote:
> 


>>> select distinct  orders.customer_id, products.product_id


>>>          from orders, products

>>> minus

>>> select distinct customer_id, product_id

>>>          from products;

>>>

>>> The first select esablishes a "universe of discourse"  for the query by

>>> joining every customer with every product. The second select excludes
>>> products that a customer did buy.
>>
>>
>>
>> The above SQL makes the solution easy to understand (should the last
>> line of the SQL be orders instead of products). Assuming the following:
>>
>> set A = {shampoo, soap, bread, wine}
>> set B = {shampoo, soap, bread}
>> set C = {wine}
>>
>> What is the most appropriate name of the function that does the
>> following:
>>
>> C = f (A, B);
>>
>> Is it NAND, NOT INTERSECTION, NOT IN? And should the order of the
>> inputs (A, B) matter?
>>
>
> Uh, isn't that 'A MINUS B' or, if you prefer, MINUS (A, B).

What about XOR(A,B) ? Received on Sat Jan 06 2007 - 14:43:27 CET