About statement "READ TABLE", we can generate code for read key dynamic as below:

DATA: BEGIN OF itab OCCURS 0,
       fld1(2),
       fld2(2),
       fld3(10),
       fld4 TYPE i,
     END OF itab,
     wa_tab LIKE itab,
     gv_key1(4) TYPE C VALUE ’FLD1’,
     gv_key2(4) TYPE C VALUE ’FLD2’. 
...
...
...
  
  READ TABLE itab INTO wa_tab
                  WITH KEY (gv_key1) = ’AA’
                           (gv_key2) = ’BB’.