SQL> DROP TABLE a;
DROP TABLE a
           *
ERROR at line 1:
ORA-00942: table or view does not exist


SQL> DROP TABLE b;

Table dropped.

SQL> CREATE TABLE a (test CHAR(4))
  2  TABLESPACE warehouse_big_data;

Table created.

SQL> CREATE TABLE b (test VARCHAR2(4))
  2  TABLESPACE warehouse_big_data;

Table created.

SQL> INSERT INTO a
  2       VALUES ('NLS');

1 row created.

SQL> INSERT INTO b
  2       VALUES ('NLS');

1 row created.

SQL> SELECT LENGTH(test), test FROM a;

LENGTH(TEST) TEST
------------ ----
           4 NLS

SQL> SELECT LENGTH(test), test FROM b;

LENGTH(TEST) TEST
------------ ----
           3 NLS

SQL> SELECT *
  2    FROM a, b
  3   WHERE a.test = b.test;

no rows selected

SQL> SELECT *
  2    FROM a, b
  3   WHERE TRIM(a.test) = TRIM(b.test);

TEST TEST
---- ----
NLS  NLS

SQL>