Creating N Copies of a Row using "CONNECT BY CONNECT_BY_ROOT"

Question

This isn't a question. I just wanted to share a technique I stumbled upon while
jamming with Vadim Tropashko on his blog recently.
Occasionally the ability to create n copies of a row is required.
For example, given a table with this data
create table t ( key integer, string varchar2(10), qty integer );
insert into t values ( 1, 'a', 2 );
insert into t values ( 2, 'b', 3 );
commit;
       KEY STRING            QTY
         1 a                   2
         2 b                   3
sometimes we need queries that produce 2 copies of row 1 and 3 copies of row 2,
like this.
       KEY STRING            QTY
         1 a                   2
         1 a                   2
         2 b                   3
         2 b                   3
         2 b                   3
A query like the following would be ideal, but unfortunately Oracle doesn't
like the existence of a CONNECT BY loop.
select key, string, qty, level from t
CONNECT BY STRING = PRIOR STRING AND LEVEL <= QTY
order by 1, 4 ;
select key, string, qty, level from t
ERROR at line 1:
ORA-01436: CONNECT BY loop in user data
Without the CONNECT BY loop we won't get the right number of rows however.
select key, string, qty, level, sys_connect_by_path( string, '/' ) path
from t
CONNECT BY LEVEL <= QTY
order by 1, 4 ;
       KEY STRING            QTY      LEVEL PATH
         1 a                   2          1 /a
         1 a                   2          2 /b/a
         1 a                   2          2 /a/a
         2 b                   3          1 /b
         2 b                   3          2 /b/b
         2 b                   3          2 /a/b
         2 b                   3          3 /b/a/b
         2 b                   3          3 /b/b/b
         2 b                   3          3 /a/a/b
         2 b                   3          3 /a/b/b
The final solution employs CONNECT_BY_ROOT to yield the desired result
without triggering an error.
select key, string, qty, level, sys_connect_by_path( string, '/' ) path
from t
CONNECT BY CONNECT_BY_ROOT KEY = KEY AND LEVEL <= QTY
order by 1, 4 ;
       KEY STRING            QTY      LEVEL PATH
         1 a                   2          1 /a
         1 a                   2          2 /a/a
         2 b                   3          1 /b
         2 b                   3          2 /b/b
         2 b                   3          3 /b/b/b
Here's an example of this "CONNECT BY CONNECT_BY_ROOT" technique in action.
It splits a comma separated value string into one row per value.
delete from t;
insert into t values( 1, 'a,bb,ccc'  , null );
insert into t values( 2, 'dddd,eeeee', null );
commit;
select
  string ,
  level as position ,
  regexp_substr( string, '[^,]+', 1, level ) as val
from
  t
connect by
  connect_by_root key = key and
  regexp_substr( string, '[^,]+', 1, level ) is not null
order by
  1, 2
STRING       POSITION VAL
a,bb,ccc            1 a
a,bb,ccc            2 bb
a,bb,ccc            3 ccc
dddd,eeeee          1 dddd
dddd,eeeee          2 eeeee--
Joe Fuda
SQL Snippets

Answer 1

Nice approach.
BTW it is just another way of workaround for CONNECT BY LOOP error.
You can also do this like:
SQL> select key, string, qty, level
  2    from t
  3  CONNECT BY STRING = PRIOR STRING
  4         AND LEVEL <= QTY
  5         and prior dbms_random.value is not null
  6   order by 1, 4;
                                    KEY STRING                                         QTY      LEVEL
                                      1 a                                                2          1
                                      1 a                                                2          2
                                      2 b                                                3          1
                                      2 b                                                3          2
                                      2 b                                                3          3
S