Can you create an internal table dynamically? (at run time)

Yes , you can create a Dynamic Internal table .Just chek out this program .

  type-pools : abap.
  field-symbols: <dyn_table> type standard table,
               <dyn_wa>,
               <dyn_field>.
  data: dy_table type ref to data,
      dy_line  type ref to data,
      xfc type lvc_s_fcat,
      ifc type lvc_t_fcat.
  selection-screen begin of block b1 with frame.
parameters: p_table(30) type c default 'T001'.
selection-screen end of block b1.
  start-of-selection.
    perform get_structure.
  perform create_dynamic_itab.      **********Creates a dyanamic internal table**********
  perform get_data.
  perform write_out.
  form get_structure.
  data : idetails type abap_compdescr_tab,
       xdetails type abap_compdescr.
  data : ref_table_des type ref to cl_abap_structdescr.
  * Get the structure of the table.
  ref_table_des ?= 
      cl_abap_typedescr=>describe_by_name( p_table ).
  idetails[] = ref_table_des->components[].
    loop at idetails into xdetails.
    clear xfc.
    xfc-fieldname = xdetails-name .
    xfc-datatype = xdetails-type_kind.
    xfc-inttype = xdetails-type_kind.
    xfc-intlen = xdetails-length.
    xfc-decimals = xdetails-decimals.
    append xfc to ifc.
  endloop.
  endform.
  form create_dynamic_itab.
  * Create dynamic internal table and assign to FS
  call method cl_alv_table_create=>create_dynamic_table
               exporting
                  it_fieldcatalog = ifc
               importing
                  ep_table        = dy_table.
    assign dy_table->* to <dyn_table>.
  * Create dynamic work area and assign to FS
  create data dy_line like line of <dyn_table>.
  assign dy_line->* to <dyn_wa>.
  endform.

  form get_data.
  * Select Data from table.
  select * into table <dyn_table>
             from (p_table).
  endform.
   Write out data from table.
  loop at <dyn_table> into <dyn_wa>.
    do.
      assign component  sy-index 
         of structure <dyn_wa> to <dyn_field>.
      if sy-subrc <> 0.
        exit.
      endif.
      if sy-index = 1.
        write:/ <dyn_field>.
      else.
        write: <dyn_field>.
      endif.
    enddo.
  endloop.

REPORT ZCLUST1 .
*
* Example: how to create a dynamic internal table
* 
* The dynamic internal table stucture
DATA: BEGIN OF STRUCT OCCURS 10,
    FILDNAME(8) TYPE C,
    ABPTYPE TYPE C,
    LENGTH TYPE I,
END OF STRUCT.

* The dynamic program source table
DATA: BEGIN OF INCTABL OCCURS 10,
    LINE(72),
END OF INCTABL.

DATA: LNG TYPE I, TYPESRTING(6).

* Sample dynamic internal table stucture
STRUCT-FILDNAME = 'field1'. STRUCT-ABPTYPE = 'c'. STRUCT-LENGTH = '6'.
APPEND STRUCT. CLEAR STRUCT.

STRUCT-FILDNAME = 'field2'. STRUCT-ABPTYPE = 'd'.
APPEND STRUCT. CLEAR STRUCT.

STRUCT-FILDNAME = 'field3'. STRUCT-ABPTYPE = 'i'.
APPEND STRUCT. CLEAR STRUCT.

* Create the dynamic internal table definition in the dyn. program
INCTABL-LINE = 'program zdynpro.'. APPEND INCTABL.
INCTABL-LINE = 'data: begin of dyntab occurs 10,'. APPEND INCTABL.

LOOP AT STRUCT.
  INCTABL-LINE = STRUCT-FILDNAME.
  LNG = STRLEN( STRUCT-FILDNAME ).

  IF NOT STRUCT-LENGTH IS INITIAL .
      TYPESRTING(1) = '('.
      TYPESRTING+1 = STRUCT-LENGTH.
      TYPESRTING+5 = ')'.
      CONDENSE TYPESRTING NO-GAPS.
      INCTABL-LINE+LNG = TYPESRTING.
  ENDIF.

  INCTABL-LINE+15 = 'type '.
  INCTABL-LINE+21 = STRUCT-ABPTYPE.
  INCTABL-LINE+22 = ','.
  APPEND INCTABL.
ENDLOOP.
INCTABL-LINE = 'end of dyntab. '.
APPEND INCTABL.

* Create the code processes the dynamic internal table
INCTABL-LINE = ' '. APPEND INCTABL.
INCTABL-LINE = 'dyntab-field1 = ''aaaaaa''.'. APPEND INCTABL.
INCTABL-LINE = 'dyntab-field1 = ''19970814''.'. APPEND INCTABL.
INCTABL-LINE = 'dyntab-field1 = 1.'. APPEND INCTABL.
INCTABL-LINE = 'append dyntab.'. APPEND INCTABL.
INCTABL-LINE = ' '. APPEND INCTABL.
INCTABL-LINE = 'loop at dyntab.'. APPEND INCTABL.
INCTABL-LINE = 'write: / dyntab.'. APPEND INCTABL.
INCTABL-LINE = 'endloop.'. APPEND INCTABL.

* Create and run the dynamic program
INSERT REPORT 'zdynpro'(001) FROM INCTABL.
SUBMIT ZDYNPRO.

or Just try out this simpler dynamic internal tables

DATA: itab TYPE STANDARD TABLE OF spfli,
              wa LIKE LINE OF itab.

DATA: line(72) TYPE c,
            list LIKE TABLE OF line(72).

START-OF-SELECTION.
*line = ' CITYFROM CITYTO '.
  line = ' AIRPTO '.
 APPEND line TO list.

SELECT DISTINCT (list)
       INTO CORRESPONDING FIELDS OF TABLE itab
           FROM spfli.

IF sy-subrc EQ 0.
  LOOP AT itab INTO wa.
*     WRITE: / wa-cityfrom, wa-cityto.
       WRITE :/ wa-airpto.
  ENDLOOP.
ENDIF.

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