PARTITION BY RANGE(NAME)
 (
  PARTITION A VALUES LESS THAN('B'),
  PARTITION B VALUES LESS THAN('C'),
  .
  .
  .
 )

SQL> DROP TABLE myemp;
Table dropped
SQL> CREATE TABLE myemp (
  2         empno   NUMBER PRIMARY KEY,
  3         ename    VARCHAR2(30),
  4         deptno   NUMBER)
  5    PARTITION BY RANGE (ename) (
  6         PARTITION pa VALUES LESS THAN('B'));
Table created
SQL> INSERT INTO myemp SELECT 122, 'ALLEN', 30 FROM dual; -- normal case, goes to correct partition
1 row inserted
SQL> INSERT INTO myemp SELECT 123, 'aLLEN', 30 FROM dual; -- won't insert
INSERT INTO myemp SELECT 123, 'aLLEN', 30 FROM dual
ORA-14400: inserted partition key does not map to any partition
SQL> INSERT INTO myemp SELECT 124, '1LLEN', 30 FROM dual; -- would get inserted, so incorrect
1 row inserted
SQL> INSERT INTO myemp SELECT 125, ' LLEN', 30 FROM dual; -- would get inserted, so incorrect
1 row inserted

SQL> SELECT * FROM myemp PARTITION (pa);
     EMPNO ENAME                              DEPTNO
---------- ------------------------------ ----------
       122 ALLEN                                  30
       124 1LLEN                                  30
       125  LLEN                                  30