If possible,try to get all data in one internal table using join statement, otherwise, sort both tables by positionid and try following code.
"if itab2 can contain multiple entries against one positionid in itab1, use:.
Loop at itab1.
Loop at itab2 where positionid = itab1-positionid.
move-corresponding itab1 to itab3.
move-corresponding itab2 to itab3.
append itab3.
clear itab3.
ENDLOOP.
ENDLOOP.
"if itab2 can contain single against one positionid in itab1, use:.
Loop at itab1.
READ table itab2 with key positionid = itab1-positionid.
move-corresponding itab1 to itab3.
move-corresponding itab2 to itab3.
append itab3.
clear itab3.
ENDLOOP.
Regards