SAP provides logical databases so as to reduce programming efforts through a kind of modularization technique. Logical databases have their own selection-screen, user authorization checks and logic for fetching data from the database so that you don't have to do it repeatedly. Just identify the right logical database for the purpose and use it. Its selection-screen will be available which you can enhance with your own fields using normal commands for creating selection-screen elements. Don't need to program authorization-checks as it is programmed there. Finally, data fetch too is done by the logical database and supplies the results into the structure with GET event, PERNR in case of PNP, for example.The link below for 'Programming utilities for the Logical databases PNP and PAP' is a guide from SAP on logical databases PNP (for employees) and PAP (for applicants) :Programming utilities for the Logical databases PNP and PAP
Reporting: Selection period and further selection help
When selecting a period you can decide between data selection period and person selection period. What does that mean?
HR Report Programming guide explaining its special features