Okay, first of all, what clueless wonder decided the proper way to return data was to concat it all into a single string?

And you're going to need to provide a few more details if you want an answer. Like, what does the table look like and what does the calling code look like.

And more likely than not, the issue will have something to do with the length of the string you are building, and not how many columns went into it.

Oh, and what are the 12-byte values that are being returned?