Difference of two sets of values

Question

I have a set of values: "foo", "bar", "blue".

I have a table which looks like this:

ID | my_col
-----------
 1 | foo
 2 | bar

I want the set values minus all available my_col values.

[foo, bar, blue] minus [foo, bar]

The result should be "blue".

How to do this in ABAP?

Answer 1

Here you are...

REPORT YYY.

TYPES string_table TYPE HASHED TABLE OF string WITH UNIQUE KEY TABLE_LINE.

DATA(gt_set1) = VALUE string_table( ( `foo` ) ( `bar` ) ( `blue` ) ).
DATA(gt_set2) = VALUE string_table( ( `foo` ) ( `bar` ) ).

DATA(gt_set1_except_set2) = FILTER string_table( gt_set1 EXCEPT IN gt_set2 WHERE table_line = table_line ).

Works however only with HASHED and SORTED tables.

Answer 2

a couple of additional examples with standard tables:

data: set type table of string, " initial set
      tab type table of string, " you table
      res type table of string. " the result

set = value #( ( `foo` ) ( `bar` ) ( `blue` ) ).
tab = value #( ( `foo` ) ( `bar` ) ).

Option 1: assuming initial set and tab are standard table you can simply loop for the initial set, and then look into your table values

In this case a full table search is done in tab table -> O(n) for tab search

LOOP AT set into data(lv_set).
  read table tab from lv_set transporting no fields.
  check sy-subrc > 0.
  append lv_set to res.
ENDLOOP.

Option 2: you can use a temporary hashed table as described in

SE38 -> Environment -> Performace examples (Intersection of internal tables)

data: htab type hashed table of string with unique key table_line.

htab = tab. " use Hashed table as temporary working table

loop at set into lv_set.

  " fast table lookup accessing with unique key O(1)
  read table htab from lv_set transporting no fields.

  check sy-subrc > 0.
  append lv_set to res.
endloop.
free htab.

Best regards !