Table transformation / field parsing in PL/SQL - sql

Question

I have de-normalized table, something like
CODES
ID | VALUE
10 | A,B,C
11 | A,B
12 | A,B,C,D,E,F
13 | R,T,D,W,W,W,W,W,S,S
The job is to convert is where each token from VALUE will generate new row. Example:
CODES_TRANS
ID | VALUE_TRANS
10 | A
10 | B
10 | C
11 | A
11 | B
What is the best way to do it in PL/SQL without usage of custom pl/sql packages, ideally with pure SQL?
Obvious solution is to implement it via cursors. Any ideas?

Answer 1

Another alternative is to use the model clause:
SQL> select id
2 , value
3 from codes
4 model
5 return updated rows
6 partition by (id)
7 dimension by (-1 i)
8 measures (value)
9 ( value[for i from 0 to length(value[-1])-length(replace(value[-1],',')) increment 1]
10 = regexp_substr(value[-1],'[^,]+',1,cv(i)+1)
11 )
12 order by id
13 , i
14 /
ID VALUE
---------- -------------------
10 A
10 B
10 C
11 A
11 B
12 A
12 B
12 C
12 D
12 E
12 F
13 R
13 T
13 D
13 W
13 W
13 W
13 W
13 W
13 S
13 S
21 rows selected.
I have written up to 6 alternatives for this type of query in this blogpost: http://rwijk.blogspot.com/2007/11/interval-based-row-generation.html
Regards,
Rob.

Answer 2

I have a pure SQL solution for you.
I adapted a trick I found on an old Ask Tom site, posted by Mihail Bratu. My adaptation uses regex to tokenise the VALUE column, so it requires 10g or higher.
The test data.
SQL> select * from t34
2 /
ID VALUE
---------- -------------------------
10 A,B,C
11 A,B
12 A,B,C,D,E,F
13 R,T,D,W1,W2,W3,W4,W5,S,S
SQL>
The query:
SQL> select t34.id
2 , t.column_value value
3 from t34
4 , table(cast(multiset(
5 select regexp_substr (t34.value, '[^(,)]+', 1, level)
6 from dual
7 connect by level <= length(value)
8 ) as sys.dbms_debug_vc2coll )) t
9 where t.column_value != ','
10 /
ID VALUE
---------- -------------------------
10 A
10 B
10 C
11 A
11 B
12 A
12 B
12 C
12 D
12 E
12 F
13 R
13 T
13 D
13 W1
13 W2
13 W3
13 W4
13 W5
13 S
13 S
21 rows selected.
SQL>

Answer 3

Based on Celko's book, here is what I found and it's working well!
SELECT
TABLE1.ID
, MAX(SEQ1.SEQ) AS START_POS
, SEQ2.SEQ AS END_POS
, COUNT(SEQ2.SEQ) AS PLACE
FROM
TABLE1, V_SEQ SEQ1, V_SEQ SEQ2
WHERE
SUBSTR(',' || TABLE1.VALUE || ',', SEQ1.SEQ, 1) = ','
AND SUBSTR(',' || TABLE1.VALUE || ',', SEQ2.SEQ, 1) = ','
AND SEQ1.SEQ < SEQ2.SEQ
AND SEQ2.SEQ <= LENGTH(TABLE1.VALUE)
GROUP BY TABLE1.ID, TABLE1.VALUE, SEQ2.SEQ
Where V_SEQ is a static table with one field:
SEQ, integer values 1 through N, where N >= MAX_LENGTH(VALUE).
This is based on the fact the the VALUE is wrapped by ',' on both ends, like this:
,A,B,C,D,
If your tokens are fixed length (like in my case) I simply used PLACE field to calculate the actual string. If variable length, use start_pos and end_pos
So, in my case, tokens are 2 char long, so the final SQL is:
SELECT
TABLE1.ID
, SUBSTR(TABLE1.VALUE, T_SUB.PLACE * 3 - 2 , 2 ) AS SINGLE_VAL
FROM
(
SELECT
TABLE1.ID
, MAX(SEQ1.SEQ) AS START_POS
, SEQ2.SEQ AS END_POS
, COUNT(SEQ2.SEQ) AS PLACE
FROM
TABLE1, V_SEQ SEQ1, V_SEQ SEQ2
WHERE
SUBSTR(',' || TABLE1.VALUE || ',', SEQ1.SEQ, 1) = ','
AND SUBSTR(',' || TABLE1.VALUE || ',', SEQ2.SEQ, 1) = ','
AND SEQ1.SEQ < SEQ2.SEQ
AND SEQ2.SEQ <= LENGTH(TABLE1.VALUE)
GROUP BY TABLE1.ID, TABLE1.VALUE, SEQ2.SEQ
) T_SUB
INNER JOIN
TABLE1 ON TABLE1.ID = T_SUB.ID
ORDER BY TABLE1.ID, T_SUB.PLACE

Answer 4

Original Answer
In SQL Server TSQL we parse strings and make a table object. Here is sample code - maybe you can translate it.
http://rbgupta.blogspot.com/2007/10/tsql-parsing-delimited-string-into.html
Second Option
Count the number of commas per row. Get the Max number of commas. Let's say that in the entire table you have a row with 5 commas max. Build a SELECT with 5 substrings. This will make it a set based operation and should be much faster than a rbar.