Workaround for mySQL subquery?

I'm needing to make a list of all customers in my database who have not purchased anything. I can't seem to think of any way but a subquery (not yet implimented) to make this work.

I have the two queries:

1. SELECT DISTINCT custid from customers
2. SELECT DISTINCT custid from orders WHERE subtot > 0 and !voided

I basically need the difference of the two.

Thanks in advance.

You'll have to do two queries since mysql does not support sub queries.

If you are using PHP you can do this:

$result=mysql_query("select distinct custid from orders where subtot>0 and !voided");
while (list($data[])=mysql_fetch_row($result)){}
$listed_ids=implode(',',$data);

$result2=mysql_query("select distinct custid from customers where custid !(in('$listed_ids'))");
while (list($nosales[])=mysql_fetch_row($result2){}

This will return the array $nosales containing the custids that have no sales.

You may be able to get by with a LEFT JOIN, but since I don't know the layout of your tables, this may be a shot in the dark

> select customers.custid
> from customers
> LEFT JOIN orders on customers.custid=orders.custid
> WHERE orders.custid IS NULL;