Precedding load creates only one table.because we can do the manipulations/aggregations/aliases with in the same load statement with another load statement.Preload is used to add dimensions and facts to the current table.
Resident load is also used to reuse already in-memory loaded tables. so here physically two table are created.
So preceding load is best practice in qlikview when comared to resident load.
load max(salary) as maxsal,
count(emp id) as count
resident tab1; //Here we used the salary and empid fields from tab1.so we need to use keyword resident.
here in data model physically both tab1 and tab2 are presented.
load *,max(salary) as maxsal,
count(emp id) as count group by empname;
If you want all the fields,you can put * .here automatically tab2 is droped itself.(without exicuting the drop command even).so here only 1 table is presented in data model.
Hope it helps!!