Question

I have a string like '00122021300123024'

I want to remove only single '0' not '00' means out put should be '001222130012324'

[NOTE : I am using ORACLE 11g regexp_replace function]

Answer 1

Without look around, search for ([123456789]|^)0([123456789]|$) and replace by $1$2 where $1 is the first capturing group and $2 the second (or \1\2).

For Oracle SQL:

select regexp_replace('00122021300123024', '([123456789]|^)0([123456789]|$)', '\1\2') from dual;

Not tested but it should work.