data modellling and changes at load script

[#1]

hi

i want to know what are the best practices when designing a data model for the qlik view and what logics should we implement at the back end instead of UI level.

for example i need to show a column 'provider' ranked and sorted on the basis of a measure amount...i need to show top 50 providers and then i have to perform calculations on another measure 'Pd_amnt'. i nee to show the sum of top50 providers,sum of pd_amnt for remining providers and total of aal as i different row??

how can i achieve that??/