I have zip code as a dimension element in the fat table , Based on the
zip codes different custonmers have different regions defines for the
dimension , how can i define a different region level for each customer
based on the zipcode?

Aj

Look up the nested set model for hierarchies or (better) buy a copy of
my book TREES & HIERARCHIES IN SQL. Each zip code grouping will be in
a table that looks like this:

CREATE TABLE AlphaRegions
(region_name CHAR(10) NOT NULL PRIMARY KEY,
start_zip CHAR(5) NOT NULL,
end_zip CHAR(5) NOT NULL,
CHECK (start_zip <= end_zip));

CREATE TABLE BetaRegions
(region_name CHAR(10) NOT NULL PRIMARY KEY,
start_zip CHAR(5) NOT NULL,
end_zip CHAR(5) NOT NULL,
CHECK (start_zip <= end_zip));

Etc. You can do any reporting hierarchy you wish with these tables.