SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(a(b(c(d(e)))))', 1, 1, 'm', 1 ) AS RESULT FROM DUAL;
RESULT
------------------------------
abcde
SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(a(b(c(d(e)))))', 1, 1, 'm', 2 ) AS RESULT FROM DUAL;
RESULT
------------------------------
bcde
SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(a(b(c(d(e)))))', 1, 1, 'm', 3 ) AS RESULT FROM DUAL;
RESULT
------------------------------
cde
SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(a(b(c(d(e)))))', 1, 1, 'm', 4 ) AS RESULT FROM DUAL;
RESULT
------------------------------
de
SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(a(b(c(d(e)))))', 1, 1, 'm', 5 ) AS RESULT FROM DUAL;
RESULT
------------------------------
e
SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(((((a)b)c)d)e)', 1, 1, 'm', 1 ) AS RESULT FROM DUAL;
RESULT
------------------------------
abcde
SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(((((a)b)c)d)e)', 1, 1, 'm', 2 ) AS RESULT FROM DUAL;
RESULT
------------------------------
abcd
SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(((((a)b)c)d)e)', 1, 1, 'm', 3 ) AS RESULT FROM DUAL;
RESULT
------------------------------
abc
SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(((((a)b)c)d)e)', 1, 1, 'm', 4 ) AS RESULT FROM DUAL;
RESULT
------------------------------
ab
SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(((((a)b)c)d)e)', 1, 1, 'm', 5 ) AS RESULT FROM DUAL;
RESULT
------------------------------
a
SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(a(b))((cd)e)', 1, 1, 'm', 1 ) AS RESULT FROM DUAL;
RESULT
------------------------------
ab
SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(a(b))((cd)e)', 1, 1, 'm', 2 ) AS RESULT FROM DUAL;
RESULT
------------------------------
b
SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(a(b))((cd)e)', 1, 1, 'm', 3 ) AS RESULT FROM DUAL;
RESULT
------------------------------
cde
SQL> SELECT REGEXP_SUBSTR( 'abcdeabcde', '(a(b))((cd)e)', 1, 1, 'm', 4 ) AS RESULT FROM DUAL;
RESULT
------------------------------
cd
SQL> SELECT REGEXP_SUBSTR( '11234567890', '(123)(4(56)(78))', 1, 1, 'm', 1 ) AS RESULT FROM DUAL;
RESULT
------------------------------
123
SQL> SELECT REGEXP_SUBSTR( '11234567890', '(123)(4(56)(78))', 1, 1, 'm', 2 ) AS RESULT FROM DUAL;
RESULT
------------------------------
45678
SQL> SELECT REGEXP_SUBSTR( '11234567890', '(123)(4(56)(78))', 1, 1, 'm', 3 ) AS RESULT FROM DUAL;
RESULT
------------------------------
56
SQL> SELECT REGEXP_SUBSTR( '11234567890', '(123)(4(56)(78))', 1, 1, 'm', 4 ) AS RESULT FROM DUAL;
RESULT
------------------------------
78
※ 그룹화는 괄호 시작'(' 부터 순서를 매긴다.