SQL>
SQL> select abs(-123), abs(0), abs(456)
2 , sign(-123), sign(0), sign(456)
3 from dual;
ABS(-123) ABS(0) ABS(456) SIGN(-123) SIGN(0) SIGN(456)
---------- ---------- ---------- ---------- ---------- ----------
123 0 456 -1 0 1
SQL>