Why not just do select NVL(SUM(MAXBYTES-BYTES),0) from DBA_DATA_FILES where TABLESPACE_NAME=:B1 and MAXBYTES <> 0 instead? You don't need a subquery here?... ********************************************************************************
SELECT NVL(SUM(MAXBYTES-BYTES),0) FROM DBA_DATA_FILES WHERE FILE_ID IN (SELECT FILE_ID FROM DBA_DATA_FILES WHERE TABLESPACE_NAME=:B1 AND MAXBYTES <> 0)
-- Alexander Fatkulin -- //www.freelists.org/webpage/oracle-l