chop part of the string

[rad_jen]

SQL> select substr('xyxxyyxxxyyyxy',-12,12) from dual;

SUBSTR('XYXX
------------
xxyyxxxyyyxy

SQL> select substr('xyxxyyxxxyyyxy',2-length('xyxxyyxxxyyyxy'),length('xyxxyyxxxyyyxy')-2) from dual;

SUBSTR('XYXX
------------
xxyyxxxyyyxy