Comparing rows

[renesis]

Hi all. I've got a table 'cartitems'. There is a column 'suppliers'. What I want to do is check whether there are various suppliers within the table. So if there are more that one supplier, the system shouldn't proceed. So I need a way to check whether or not all the values in a column are the same.
Any ideas?

[devinemke]

SELECT DISTINCT suppliers FROM cartitems

if the above query returns more than 1 row then there are multiple suppliers