Checking oracle sid and database name

Question

I want to check SID and current database name.

I am using following query for checking oracle SID

select instance from v$thread;

bu

Answer 1

Type on sqlplus command prompt

SQL> select * from global_name;

then u will be see result on command prompt

SQL ORCL.REGRESS.RDBMS.DEV.US.ORACLE.COM

Here first one "ORCL" is database name,may be your system "XE" and other what was given on oracle downloading time.