In SQL you can get a list of unique values of a field using DISTINCT. When the data is already in an internal table, before ABAP 7.40 you had to use a LOOP and a COLLECT.
But now that we live in more modern times, there is a simpler and more elegant way to achieve the same with a single command.
TYPES ty_t_land1 TYPE STANDARD TABLE OF land1 WITH KEY table_line. SELECT * FROM kna1 INTO TABLE @data(t_kna1). DATA(t_land1) = VALUE ty_t_land1( FOR GROUPS land1 OF wa IN t_kna1 GROUP BY wa-land1 ASCENDING WITHOUT MEMBERS ( land1 ) ).
Greetings from Abapinho.