N-TILE query without function

[deltaair]

Hello,

I have a table with 3 fields
id_person, id_event, value

I need to divide all id_person(s) into deciles/quartiles.
I am using ANSI SQL on Netezza and it does not support the Quartile/Ntile functions.

How can I write a manual query to give me a list of
id_persons, sorted in descending order of value, and a 3rd field with the ncile they fall into based on their value.

Thanks,
Manik