Script to find foreign key constraints

Script to find foreign key constraints
select owner,constraint_name,constraint_type,table_name,r_owner,r_constraint_name
from all_constraints
where constraint_type='R'
and r_constraint_name in (select constraint_name from all_constraints
where constraint_type in ('P','U') and table_name='&TABLE_NAME')
/

Find Oracle Database Character Set

Character Sets
(Ordinary) character set
The (ordinary) character set for a database can be determined with:

SQL> select value from nls_database_parameters where parameter = 'NLS_CHARACTERSET';

National character set
The national character set for a database can be determined with:

SQL> select value from nls_database_parameters
where parameter = 'NLS_NCHAR_CHARACTERSET';