If you run something like
SELECT * FROM tng_people ORDER BY personID LIMIT 10;,
you get a result list with I10, I100, I1000, I10000 and so on. For sorting by ID as a number, use
...ORDER BY CAST(SUBSTRING(personID, 2) AS UNSIGNED)...
instead. (SUBSTRING deletes the first character ("I"), CAST converts the remaining string into a number.)