Split string in Oracle with regexp_substr in order

Question

I have a string in Oracle database, my string is: 'bbb;aaa;qqq;ccc'

I used regexp for split my string:

select distinct trim(regexp_substr('bbb;aaa;qqq;ccc','[^;]+', 1,level) ) as q 
from dual
connect by regexp_substr('bbb;aaa;qqq;ccc', '[^;]+', 1, level) is not null ;

I want to split it in order, I expected the below output always:

bbb
aaa
qqq
ccc

because order of the subString are very important for me. but the result of this query is not in order:

qqq
aaa
bbb
ccc

Answer 1

You don't need a DISTINCT to get your result; besides, to get the result in a given order, all you need is an ORDER BY clause:

select trim(regexp_substr('bbb;aaa;qqq;ccc','[^;]+', 1,level) ) as q 
from dual
connect by regexp_substr('bbb;aaa;qqq;ccc', '[^;]+', 1, level) is not null
order by level

Answer 2

If you do need DISTINCT:

WITH your_data( value ) AS (
  SELECT 'bbb;aaa;qqq;ccc;aaa;eee' FROM DUAL
),
positions ( string, lvl, start_pos, end_pos ) AS (
  SELECT value, 1, 1, INSTR( value, ';', 1, 1 ) FROM your_data
UNION ALL
  SELECT string, lvl + 1, end_pos + 1, INSTR( string, ';', 1, lvl + 1 )
  FROM positions
  WHERE  end_pos > 0
),
substrings ( string, substring, lvl, start_pos ) AS (
  SELECT string,
         DECODE( end_pos, 0, SUBSTR( string, start_pos ), SUBSTR( string, start_pos, end_pos - start_pos ) ),
         lvl,
         start_pos
  FROM   positions
)
SELECT string,
       substring,
       lvl
FROM   substrings
WHERE  INSTR( ';' || string || ';', ';' || substring || ';' ) = start_pos;

Output:

STRING                  SUBSTRING                      LVL
----------------------- ----------------------- ----------
bbb;aaa;qqq;ccc;aaa;eee bbb                              1
bbb;aaa;qqq;ccc;aaa;eee aaa                              2
bbb;aaa;qqq;ccc;aaa;eee qqq                              3
bbb;aaa;qqq;ccc;aaa;eee ccc                              4
bbb;aaa;qqq;ccc;aaa;eee eee                              6