I have input string something like :
1.2.3.4_abc_4.2.1.44_1.3.4.23
100.11.11.22_xyz-abd_10.2.1.2_12.2.3.4
100.11.11.22_xyz_123_10.2.1.2_1.2.3.4
I have to replace the first string formed between two ipaddress which are separated by _, however in some string the _ is part of the replacement string (xyz_123)
I have to find the abc, xyz-abd and xyz_123 from the above string, so that I can replace with another column in that table.
_.*?_(?=\d+\.)
matches _abc_, _xyz-abd_ and _xyz_123_ in your examples. Is this working for you?
DECLARE
result VARCHAR2(255);
BEGIN
result := REGEXP_REPLACE(subject, $$_.*?_(?=\d+\.)$$, $$_foo_$$);
END;
Probably this is enough:
_[^.]+_
and replace with
_Replacement_
See it here on Regexr.
[^.]+ uses a negated character class to match a sequence of at least one (the + quantifier) non "." characters.
I am also matching a leading and a trailing "_", so you have to put it in again in the replacement string.
If PostgreSQL supports lookbehind and lookahead assertions, then it is possible to avoid the "_" in the replacement string:
(?<=_)[^.]+(?=_)
In order to map match first two "" , as @stema and @Tim Pietzcker mentioned the regex works. Then in order to append "" to the column , which is what I was struggling with, can be done with || operator as eg below
update table1 set column1=regexp_replace(column1,'.*?(?=\d+.)','' || column2 || '_')
Then for using the another table for update query , the below eg can be helpfull
update table1 as t set column1=regexp_replace(column1,'.*?(?=\d+.)','' || column2 || '_') from table2 as t2 where t.id=t2.id [other criteria]
