Check if value inside a column of an internal table exist in a sap table (ex: check vendors from an excel file)

it_column_exist_in_table.abap

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"" check it column value exist in sap

TYPES: BEGIN OF s_struct,
         vendor TYPE lifnr,
       END OF s_struct.

DATA: sap_data TYPE HASHED TABLE OF s_struct WITH UNIQUE KEY vendor.
DATA: data_to_verify TYPE TABLE OF s_struct.

SELECT lifnr AS vendor
  FROM lfa1
  INTO CORRESPONDING FIELDS OF TABLE data_to_verify.

"" S1 - 75ms
"" Complexity : O(logn + n)

SELECT
    lifnr AS vendor
  FROM lfa1
  INTO CORRESPONDING FIELDS OF TABLE @sap_data. "" O(logn)
"where

LOOP AT data_to_verify ASSIGNING FIELD-SYMBOL(<fs_vendor>). "" O(n)
  IF VALUE #( sap_data[ vendor = <fs_vendor>-vendor ] OPTIONAL ) IS NOT INITIAL. "" O(1)
    "" Exist
  ELSE.
    "" Don't exist
  ENDIF.
ENDLOOP.

"" S2 - 134ms

DATA: r_lifnr TYPE HASHED TABLE OF lifnr_ran WITH UNIQUE KEY low.

"" Add value on low
r_lifnr = CORRESPONDING #( data_to_verify MAPPING low = vendor ).
"" Add sign & option
MODIFY r_lifnr FROM VALUE #( sign = 'I' option = 'EQ' ) TRANSPORTING sign option WHERE low <> ''.

SELECT COUNT(*)
  FROM lfa1
  WHERE lifnr IN @r_lifnr
  INTO @DATA(nb_vendor).

IF nb_vendor <> lines( r_lifnr ).
  "" some vendor dont exist
ELSE.
  "" all vendors exist
ENDIF.