This is report of these bugs like results of SQL in Oracle11gR2.
I hoped that these bugs like results are fixed in Oracle11gXE.
But it seems both SQL engines are same :_|
select * from v$version;
BANNER
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Oracle Database 11g Express Edition Release 11.2.0.2.0 - Beta
PL/SQL Release 11.2.0.2.0 - Beta
CORE 11.2.0.2.0 Production
TNS for 32-bit Windows: Version 11.2.0.2.0 - Beta
NLSRTL Version 11.2.0.2.0 - Production