framework/resources/Functional/joins/nulleqjoin/nullEqJoin_15.q

select t1.c4 
from `t_alltype.parquet` t1, `t_alltype.parquet` t2 
where t1.c4 = t2.c4 OR (t1.c4 IS NULL AND t2.c4 IS NULL)
ORDER BY t1.c4 NULLS LAST;