Code :
REPORT ZVP_SELECT_SUM_GROUP_BY.

TYPES: BEGIN OF TY_VBAP,
         VBELN TYPE VBAP-VBELN,
         CMPRE TYPE VBAP-CMPRE,
       END OF TY_VBAP.

DATA: IT       TYPE TABLE OF TY_VBAP,
      WA       TYPE TY_VBAP,

      LV_VBELN TYPE VBAP-VBELN.

SELECT-OPTIONS: S_VBELN FOR LV_VBELN.

SELECT VBELN
       SUM( CMPRE )
  FROM VBAP INTO TABLE IT UP TO 20 ROWS WHERE VBELN IN S_VBELN GROUP BY VBELN.

IF SY-SUBRC EQ 0.
  WRITE:/ 'VBELN', '             CMPRE'.
  LOOP AT IT INTO WA.
    WRITE:/ WA-VBELN,
    WA-CMPRE.

  ENDLOOP.
ENDIF.

Output :

sum of the CMPRE values with corresponding to same VBELN values.

IDE Used To Test This Code : ABAP Editor.

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