SQL INSTR() using CSV. Need exact match rather than part

Question

This is a follow up issue relating to the answer for http://stackoverflow.com/questions/2445029/sql-placeholder-in-where-in-issue-inserted-strings-fail

Quick background: We have a SQL query that uses a placeholder value to accept a string, which represents a unique tag/id. Usually, this is only a single tag, but we needed the ability to use a csv string for multiple tags, returning a combined result.

In the answer we received from the vendor, they suggested the use of the INSTR function, ala:

select *  
from pitotal  
where tag IN (SELECT tag from pipoint WHERE INSTR(?, tag) <> 0) and time between 'y' and 't'

This works perfectly well 99% of the time, the issue is when the tag is also a subset of 2 parts of the CSV string. Eg the placeholder value is: 'northdom,southdom,eastdom,westdom'

and possible tags include: north or northdom

What happens, as north is a subset of northdom, is that the two tags are return instead of just northdom, which is actually what we want.

I'm not strong on SQL so I couldn't work out how to set it as exact, or split the csv string, so help would be appreciated.

Is there a way to split the csv string or make it look for an exact match?

Answer 1

If you use a query like this it should work. Given that you surround the tag with commas.

select *  
from pitotal  
where tag IN (SELECT tag from pipoint WHERE INSTR(?, ',' || tag || ',') <> 0) and time between 'y' and 't'

Basically... instead of searching for north we'll be searching for ,north,. And instead of searching in northdom,southdom,eastdom,westdom we'll search in ,northdom,southdom,eastdom,westdom,