Use ABS in PL/SQL statement
SQL> SQL> set serveroutput on SQL> SQL> SQL> BEGIN 2 DBMS_OUTPUT.PUT_LINE(ABS(3.5)); 3 DBMS_OUTPUT.PUT_LINE(ABS(-3.5)); 4 DBMS_OUTPUT.PUT_LINE(ABS(0)); 5 END; 6 / 3.5 3.5 0 PL/SQL procedure successfully completed. SQL> SQL>