framework/resources/Functional/joins/nulleqjoin/nullEqJoin_19.q

select t1.columns[0], t2.columns[0] 
from `oneColDupsWnulls.csv` t1, `oneColWOnulls.csv` t2 
WHERE t1.columns[0] = t2.columns[0] OR ( t1.columns[0] IS NULL AND t2.columns[0] IS NULL );