Querying substrings against a list of values - sql

Question

I'm reading from a dataset that I unfortunately don't have the access to modify. It has concatenated strings of values, and I want to select records for which any of those substrings (as split by a given character) matches any of the values in a specific list. I'll be passing the queries in via Python, so it won't be compared against a static list.
For example, the table looks like:
CrappyColumn
-----------
1;2
4
1
2;1
1;3
2
And I might want to return anything that has 2 or 4 in it. So, my result should be:
1;2
4
2
2;1
I have played with regexp_substr and gotten something that actually works; however, it just runs indefinitely (as much as 10 minutes before I give up) when I run it on the full dataset (which only includes about three thousand records with values that are often a couple hundred characters long). I need something that works in a reasonable amount of time for repeated execution.
I realize that--even with a variable comparison list--I could just write my Python code to parse the list and construct multiple LIKE statements, but that seems inefficient, and I assume that there is a better way.
And here's what I've done that takes too long:
SELECT DISTINCT CrappyColumn
FROM
(SELECT DISTINCT CrappyColumn, regexp_substr(CrappyColumn, '[^;]+', 1, LEVEL) as UGH
FROM CrappyTable
CONNECT BY regexp_substr(CrappyColumn, '[^;]+', 1, LEVEL) IS NOT NULL)
WHERE UGH IN ('2', '4')
Is there a better, faster, cleaner way to accomplish this?
EDIT - RESOLUTION:
Thanks to vkp's help, here is what I implemented:
regexp_like(SITE_ID, '^(2|4)(:)|(:)(2|4)(:)|(:)(2|4)$|^(2|4)$')
I modified it for my final product, so that it can handle strings of more than one character--by changing [2|4] to (2|4). This works in cases of searching for numbers that aren't single-digit.

Answer 1

You can use like:
select t.*
from crappytable t
where ';' || crappycolumn || ';' like '%;2;%' or
';' || crappycolumn || ';' like '%;4;%';
You seem to know that storing lists of values in a single column is a bad idea, so I'll spare the harangue ;)
EDIT:
If you don't like like, you can use regexp_like() like this:
where regexp_like(';' || crappycolumn || ';', ';2;|;4;')

Answer 2

A simpler method would be to use regexp_like to check if the list has 2 or 4 in it.
select *
from tablename
where regexp_like(crappycolumn,'^[2|4][^0-9]|[^0-9][2|4][^0-9]|[^0-9][2|4]$|^[2|4]$')
^[2|4][^0-9] - Starts with 2 or 4 not followed by a digit.
[^0-9][2|4][^0-9] - 2 or 4 not succeeded or preceded by a digit.
[^0-9][2|4]$ - Ends with 2 or 4 not preceded by a digit.
^[2|4]$ - 2 or 4 is the only character in the string.

Answer 3

Another form of regexp_like(). This regex looks for 2 or 4 only when proceeded by the beginning of the line or a semi-colon and when followed by a semi-colon or the end of the line:
SQL> with crappy_tbl(crappy_col) as (
select '1;2' from dual union
select '4' from dual union
select '1' from dual union
select '2;1' from dual union
select '1;3' from dual union
select '2' from dual union
select '22;;44;' from dual
)
select crappy_col
from crappy_tbl
where regexp_like(crappy_col, '(^|;)(2|4)(;|$)');
CRAPPY_
-------
1;2
2
2;1
4
SQL>