1 *modifying a set of lines directly（批量修改内表数据）
 2 *使用"LOOP ... ASSIGNING ..."可以直接修改内表中的数据，而不需要先将内表数据复制到相应工作区，然后再更新回去。
 3 ***METHOD ONE:
 4 LOOP AT itab INTO wa.
 5   i = sy-tabix MOD 2.
 6   IF i = 0.
 7     wa-flag = ‘X‘.
 8     MODIFY itab FROM wa.
 9   ENDIF.
10 ENDLOOP.
11 
12 ***METHOD TWO:
13 field-symboles:<wa> like itab.
14 LOOP AT itab ASSIGNING <wa>.
15   i = sy-tabix MOD 2.
16   IF i = 0.
17     <wa>-flag = ‘X‘.
18   ENDIF.
19 ENDLOOP.
20 
21 ***METHOD THERE:
22 DATA: gt_list TYPE TABLE OF ty_list.
23 FIELD-SYMBOLS <fs_list> TYPE ty_list.
24 CASE <fs_list>-wbstk.
25   WHEN ‘C‘.
26     <fs_list>-status = icon_led_green.
27   WHEN ‘B‘.
28     <fs_list>-status = icon_led_yellow.
29   WHEN ‘A‘.
30     <fs_list>-status = icon_led_red.
31 ENDCASE.
32 ENDLOOP.