Backreference : REGEXP_SUBSTR « Regular Expressions Functions « Oracle PL/SQL Tutorial

1. Oracle PL/SQL Tutorial
2. Regular Expressions Functions
3. REGEXP_SUBSTR

The backslash may be followed by a number.
In the backreference version, "\1" says to match the same string as was matched by the nth subexpression.

As a first example, we can use the backreference in a manner similar to the repeat operator.


SQL>
SQL> SELECT REGEXP_SUBSTR('Yababa dababa do','(ab)')
  2  FROM dual;

RE
--
ab

SQL>
SQL>
SQL> SELECT REGEXP_SUBSTR('Yababa dababa do','(ab)\1')
  2  FROM dual;

REGE
----
abab

SQL>
SQL>
SQL> SELECT REGEXP_SUBSTR('Yababa dababa do','(ab){2}') from dual;

REGE
----
abab

SQL>