To fill an internal table in native SQL, use OPEN cursor, FETCH NEXT cursor, CLOSE cursor statements, look a the sample at http://help.sap.com/abapdocu_731/en/abapexec_cursor.htm.
(Native SQL doesn't know anything of Abap internal table 
)
For better select statement, check Oracle forums for threads like query to check tablespace size and freespace in https://forums.oracle.com/.
Regards,
Raymond