原文連結：https://blog.csdn.net/lmf496891416/article/details/111317377

1.格式：

  LOOP AT 內表  INTO DATA(工作區)  GROUP BY ( 欄位  = 工作區-欄位
                                   size  = GROUP SIZE  "分組組數--
                                   index = GROUP INDEX ) "分組的組序號
  ASCENDING    ASSIGNING FIELD-SYMBOL(<組>).

  
 
LOOP AT GROUP <組> ASSIGNING FIELD-SYMBOL(<指標>).
     "對指標進行操作，和普通的loop迴圈相似
  ENDLOOP.

ENDLOOP.

2.簡而言之：就是第一個loop迴圈是把內表進行分組，第二loop迴圈是把組裡的資料迴圈讀出來進行修改判斷等操作。
3.可以替代AT END OF /AT NEW OF。
4.具體例項-複製就能用

TYPES: BEGIN OF ty_employee,
         name TYPE char30,
         role TYPE char30,
         age  
 
TYPE i,
         sex  TYPE char10,
       END OF ty_employee,
ty_employee_t TYPE STANDARD TABLE OF ty_employee WITH KEY name.
       "對內表進行賦值"
DATA(gt_employee) = VALUE ty_employee_t(   
( name = 'John'     role = 'ABAP guru'       age = 34  sex =  'MAN'   )
( name = 'Alice'     role = 'FI Consultant
 
'   age = 42  sex =  'WOMAN'  )
( name = 'Barry'    role = 'ABAP guru'       age = 54   sex =  'WOMAN'  )
( name = 'Mary'     role = 'FI Consultant'   age = 37  sex =  'WOMAN' )
( name = 'Arthur'   role = 'ABAP guru'       age = 34  sex =  'MAN'  )
( name = 'Mandy'   role = 'SD Consultant'     age = 64  sex =  'MAN'  ) ).

DATA: gv_tot_age TYPE i,
      gv_avg_age TYPE decfloat34.
"通過角色進行分組"
LOOP AT gt_employee INTO DATA(ls_employee) GROUP BY ( role  = ls_employee-role
                                           size  = GROUP SIZE  "分組組數"
                                           index = GROUP INDEX ) "分組的組序號"
  ASCENDING    ASSIGNING FIELD-SYMBOL(<group>).
  
  CLEAR: gv_tot_age.
  WRITE: / | 組序號: { <group>-index }    角色: { <group>-role WIDTH = 15 }|
              & |     這個組有幾條資料: { <group>-size  } |.
   "loop迴圈組，將組裡的資料讀出來"           
  LOOP AT GROUP <group> ASSIGNING FIELD-SYMBOL(<ls_member>).
    gv_tot_age = gv_tot_age + <ls_member>-age.
    WRITE: /13 <ls_member>-name .
  ENDLOOP.
  
  gv_avg_age = gv_tot_age / <group>-size.
  WRITE: / |組平均年齡: { gv_avg_age }|.
  SKIP.
ENDLOOP.

例項最終結果圖：