there are 2 tables..
IF there is something in the table1.cpaytono field, a reference record will be in the table2 table.
There may be multiple records in the table2 table for each record in the table1 table.
Does the below query prove that every cpaytono in table1 has a record in table2:
select * from table1 where cpaytono <> '' and cpaytono not in (select caddrno from table2 where cvendno = table1.cvendno)..