Parse Values with Delimiters Using REGEXP_SUPSTR in Oracle 10g - oracle

Question

I have a table called TVL_DETAIL that contains column TVL_CD_LIST. Column TVL_CD_LIST contains three records:
TVL_CD_LIST:
M1180_Z6827
K5900_Z6828
I2510
I've used the following code in an attempt to return the values only(so excluding the underscore):
SELECT
TVL_CD_LIST
FROM TVL_DETAIL
WHERE TVL_CD_LIST IN (SELECT regexp_substr(TVL_CD_LIST,'[^_]+', 1, level) FROM DUAL
CONNECT BY regexp_substr(TVL_CD_LIST,'[^_]+', 1, level) IS NOT NULL)
What I was expecting to see returned in separate rows was:
M1180
Z6827
K5900
Z6828
I2510
But it only returns I2510(which is the original value that doesn't contain an underscore).
What am I doing wrong? Any help is appreciated. Thanks!

Answer 1

To answer your question, you are querying for the list where it matches a sub-element and that will only happen where the list is comprised of one element. What you really wanted to select are the sub-elements themselves.
Note: Explanation of why parsing strings using the regex form '[^_]+' is bad here: https://stackoverflow.com/a/31464699/2543416
You want to parse the list, selecting the elements:
SQL> with TVL_DETAIL(TVL_CD_LIST) as (
select 'M1180_Z6827' from dual union
select 'K5900_Z6828' from dual union
select 'I2510' from dual
)
SELECT distinct regexp_substr(TVL_CD_LIST, '(.*?)(_|$)', 1, level, NULL, 1) element
FROM TVL_DETAIL
CONNECT BY level <= LENGTH(regexp_replace(TVL_CD_LIST, '[^_]', '')) + 1;
-- 11g CONNECT BY level <= regexp_count(TVL_CD_LIST, '_') + 1;
ELEMENT
-----------
Z6827
K5900
M1180
I2510
Z6828
SQL>
And this is cool if you want to track by row and element within row:
SQL> with TVL_DETAIL(row_nbr, TVL_CD_LIST) as (
select 1, 'M1180_Z6827' from dual union
select 2, 'K5900_Z6828' from dual union
select 3, 'I2510' from dual
)
SELECT row_nbr, column_value substring_nbr,
regexp_substr(TVL_CD_LIST, '(.*?)(_|$)', 1, column_value, NULL, 1) element
FROM TVL_DETAIL,
TABLE(
CAST(
MULTISET(SELECT LEVEL
FROM dual
CONNECT BY level <= LENGTH(regexp_replace(TVL_CD_LIST, '[^_]', '')) + 1
-- 11g CONNECT BY LEVEL <= REGEXP_COUNT(TVL_CD_LIST, '_')+1
) AS sys.OdciNumberList
)
)
order by row_nbr, substring_nbr;
ROW_NBR SUBSTRING_NBR ELEMENT
---------- ------------- -----------
1 1 M1180
1 2 Z6827
2 1 K5900
2 2 Z6828
3 1 I2510
SQL>
EDIT: Oops, edited to work with 10g as REGEXP_COUNT is not available until 11g.

Answer 2

The query you have used creates the list but you are comparing the list of record with column it self using the in clause, as such M1180 or Z6827 cannot be equal to M1180_Z6827 and so for K5900_Z6828. I2510 has only one value so it gets matched.
You can use below query if your requirement is exactly what you have mentioned in your desired output.
SQL> WITH tvl_detail AS
2 (SELECT 'M1180_Z6827' tvl_cd_list FROM dual
3 UNION ALL
4 SELECT 'K5900_Z6828' FROM dual
5 UNION ALL
6 SELECT 'I2510' FROM dual)
7 ---------------------------
8 --- End of data preparation
9 ---------------------------
10 SELECT regexp_substr(tvl_cd_list, '[^_]+', 1, LEVEL) AS tvl_cd_list
11 FROM tvl_detail
12 CONNECT BY regexp_substr(tvl_cd_list, '[^_]+', 1, LEVEL) IS NOT NULL
13 AND PRIOR tvl_cd_list = tvl_cd_list
14 AND PRIOR sys_guid() IS NOT NULL;
OUTPUT:
TVL_CD_LIST
--------------------------------------------
I2510
K5900
Z6828
M1180
Z6827