You use the KEEP statement.
See below where two datasets are created, one with Name/Age/Sex and second with Name/Weight/Height.
When you create the datasets, it's likely you'll want a common variable between the two so you can map back to records if required.
data class1;
set sashelp.class;
keep name age sex;
run;
data class2;
set sashelp.class;
keep name weight height;
run;
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