in reply to retrive data from another file by comparing the values
It would be easier to offer advice if you provided more information, like what the problem you are trying to solve is, and what you've tried so far. The snippet you posted would make more sense with some context. Although it's possible to read it and understand what it's doing, it's easier to do so if we know WHY it's doing what it's doing.
Also with a description of the problem, you might be offered a better solution than what you're pursuing; quite often I'll see a writeup and think, "Why, that's easy, you just do X!". I'll go into the node to reply as such, and someone else will have said "Why, that's easy! You just do Y!" - and it turns out Y is much easier and makes more sense than X.
A sample of your data and a description of what it is and what it means would probably be helpful, too.