How to fix the Oracle error ORA-12727: invalid back reference in regular expression?

In this post, you’ll learn more about the Oracle ErrorORA-12727: invalid back reference in regular expression with the details on why you receive this error and the possible solution to fix it.

Oracle Error Description

ORA-12727: invalid back reference in regular expression

Reason for the Error ORA-12727: invalid back reference in regular expression

A back references was found before a sub-expression.

How to fix the Error ORA-12727: invalid back reference in regular expression ?

You can fix this error in Oracle by following the below steps

Ensure a valid sub-expression is being referenced.