Why is Oracle's to_char() function adding spaces?

Question

Why is Oracle\'s to_char() function adding spaces?

select length(\'012\'), 
       length(to_char(\'012\')), 
       length(to_char(\'12\', \'000\')         


        

Answer 1

The extra leading space is for the potential minus sign. To remove the space you can use FM in the format:

SQL> select to_char(12,'FM000') from dual;

TO_C
----
012

By the way, note that to_char takes a NUMBER argument; to_char('012') is implicitly converted to to_char(to_number('012')) = to_char(12)