SPQuery: How to check for blank fields?

Query to filter empty SharePoint fields:

                SPQuery query = new SPQuery();

                query.Query = "<Where>" +

                    "<Or>" +
                    "<IsNotNull><FieldRef Name='Hobbies'/></IsNotNull>" +
                    "<Neq><FieldRef Name='Hobbies'/><Value Type='Text'></Value></Neq>" +
                    "</Or>" +

                    "</Where>" +
                    "<OrderBy>" +
                    "<FieldRef Name='Created' Ascending='FALSE' />" +
                     "</OrderBy>";