How to display rows that when added together equal zero

Question

Been searching for a few weeks for a solution to this but have come up blank.

I have table of data similar to this:

client_ref  supplier_key  client_amou         


        

Answer 1

SELECT 
    * 
FROM 
    tbis
INNER JOIN
(
    SELECT
        client_ref, supplier_key
    FROM
        tbis
    GROUP by client_ref, supplier_key
    HAVING sum(client_amount) = 0
) match
ON match.client_ref = tbis.client_ref 
AND match.supplier_key = tbis.supplier_key

Demo at http://sqlfiddle.com/#!3/a3447/8/0