Remove zeros only to left of number

Question

Hi,
I want a function that will remove 0 characters only to the left of a number. However the number is in string format.
For example, I want to replace the following string:
'00000010200'
to be
'10200'
I understand that REPLACE('00000010200','0') would remove all 0 characters.
Can anyone provide a solution to this?

Answer 1

You have two basic approaches given, one uses implicit type conversion, the other string manipulation. The main difference will be what happens when you have none numeric data in the column.
If the column is a text data type, you will get none numeric data in there at some time, at which point the string manipulation approaches will continue and return the none numeric data regardless, while the type conversion approach will raise an exception and fail.
Neither behavior is inherently more desirable, but will need to be considered within the context of the business requirement.
SQL> create table t (s varchar2(10));
Table created.
SQL> insert into t select lpad(level * 10, 10, '0') from dual
  2    connect by level <= 3;
3 rows created.
SQL> insert into t values ('Boo!');
1 row created.
SQL> select s, ltrim(s, '0') from t;
S          LTRIM(S,'0
0000000010 10
0000000020 20
0000000030 30
Boo!       Boo!
SQL> select s, s * 1 from t;
ERROR:
ORA-01722: invalid number
no rows selected
SQL> select s, to_number(s) from t;
ERROR:
ORA-01722: invalid number
no rows selected
SQL> select s, trunc(s) from t;
ERROR:
ORA-01722: invalid number
no rows selected
SQL>