Need to understand regexp_replace logic of given code

Asked Jun 07 '17 at 18:05

Active Jun 07 '17 at 18:14

Viewed 23 times

I going through a oracle code and found this code:

Query 1:

SELECT RTRIM (REGEXP_REPLACE ('ABC,CDE,ABC','([^,]*)(,\1)+($|,)','\1\3'),',') FROM DUAL;

Output 1:

ABC,CDE,ABC

Query 2:

SELECT RTRIM (REGEXP_REPLACE ('ABC,ABC,CDE','([^,]*)(,\1)+($|,)','\1\3'),',') FROM DUAL;

Output 2:

ABC,CDE

Query 3:

SELECT RTRIM (REGEXP_REPLACE ('ABC,ABC,CDE,CDE,ABC,CDE','([^,]*)(,\1)+($|,)','\1\3'),',') FROM DUAL;

Output 3:

ABC,CDE,ABC,CDE

though I know what this regexp_replace is doing but I need to understand what this regexp_replace is doing step by step and what it mean by each key word.I am able to find usage of individual syntax part but can't decipher it with combination.

Also if there is any website/book available to learn such complex usage of regexp_replace function, it would be great help.

edited Jun 07 '17 at 18:14

lit

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asked Jun 07 '17 at 18:05

ravi agrawal

What did google tell you when you searched for regex resources? – Soviut Jun 07 '17 at 18:10
1

[Regex 101](https://www.regex101.com/) is a great website to understand a specific regexp. :) – rbock Jun 07 '17 at 18:13
1

Although Oracle regex is a bit specific, your regex can be checked at https://regex101.com/r/r9V7tH/1 - it works just the same with PCRE engine. – Wiktor Stribiżew Jun 07 '17 at 18:13

Need to understand regexp_replace logic of given code

0 Answers0