ABAP Select data from SAP table CAT_C2NTB into internal table

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Below is a number of ABAP code snippets to demonstrate how to select data from SAP CAT_C2NTB table and store it within an internal table, including using the newer @DATA inline declaration methods. It also shows you various ways to process this data using ABAP work area, inline declaration or field symbols including executing all the relevant CONVERSION_EXIT routines specific to CAT_C2NTB. See here for more generic Select statement tips.

Sometimes data within SAP is stored within the database table in a different format to what it is displayed to the user. These input/output conversation FM routines are what translates the data between the two formats.

There is also a full declaration of the CAT_C2NTB table where each field has a char/string type for you to simply copy and paste. This allows you to use processing that is only available to these field types such as the CONCATENATE statement.

DATA: IT_CAT_C2NTB TYPE STANDARD TABLE OF CAT_C2NTB,
      WA_CAT_C2NTB TYPE CAT_C2NTB,
      GD_STR TYPE STRING.

DATA: lo_typedescr type REF TO cl_abap_typedescr.
DATA: lv_fieldname type fieldname.

FIELD-SYMBOLS: <FIELD> TYPE any.
FIELD-SYMBOLS: <CAT_C2NTB> TYPE CAT_C2NTB.

*Process all fields in table header/work area as string values
  PERFORM process_as_string_field_values CHANGING wa_CAT_C2NTB.

SELECT *
*restrict ABAP select to first 10 rows
 UP TO 10 ROWS      
  FROM CAT_C2NTB
  INTO TABLE IT_CAT_C2NTB.

*Select data and declare internal table using in-line method @DATA
*SELECT *
*  FROM CAT_C2NTB
*  INTO TABLE @DATA(IT_CAT_C2NTB2).
*--Further methods of using ABAP code to  select data from SAP database tables

*You can also declare the header/work area using the in-line DATA declaration method
READ TABLE IT_CAT_C2NTB INDEX 1 INTO DATA(WA_CAT_C2NTB2).


*Demonstrate how to loop at an internal table and update values using a FIELD-SYMBOL
LOOP AT IT_CAT_C2NTB ASSIGNING <CAT_C2NTB>.

*To update a field value using a field symbol simply change the value via the field symbol pointer
<CAT_C2NTB>-TABLE = 1.
<CAT_C2NTB>-KEYFLAG = 1.
<CAT_C2NTB>-FNAME = 1.
<CAT_C2NTB>-OFFSET = 1.
<CAT_C2NTB>-DDLEN = 1.

ENDLOOP.

LOOP AT IT_CAT_C2NTB INTO WA_CAT_C2NTB.
*Write horizonal line to screen report.
  WRITE:/ sy-uline.

*Write selected data to screen/report before conversion.
  WRITE:/ sy-vline,   WA_CAT_C2NTB-INTLEN, sy-vline,
  WA_CAT_C2NTB-DECIMALS, sy-vline,
  WA_CAT_C2NTB-DATATYPE, sy-vline,
  WA_CAT_C2NTB-INTTYPE, sy-vline,
  WA_CAT_C2NTB-FIELDTEXT, sy-vline,
ENDLOOP.
   
*Add any further fields from structure WA_CAT_C2NTB you want to display...

  WRITE:/ sy-uline.
* Aternatively use generic code to Write field values (and NAME) to screen report
  DO.
    ASSIGN COMPONENT sy-index OF STRUCTURE wa_CAT_C2NTB TO <field>.
    IF sy-subrc <> 0. EXIT. ENDIF.
    WRITE:/ 'Field Value', <field>, sy-vline.
    gd_str = <field> .
    lo_typedescr ?= CL_ABAP_DATADESCR=>DESCRIBE_BY_DATA( <field> ).
    lv_fieldname = lo_typedescr->GET_RELATIVE_NAME( ).
    WRITE:/ 'Field Name', lv_fieldname.
  ENDDO.

  
*Redo loop but convert all fields from internal to out value  
LOOP AT IT_CAT_C2NTB INTO WA_CAT_C2NTB.


*Write horizonal line to screen report.
  WRITE:/ sy-uline.

*Convert all fields to display/output versions using conversion routines
  PERFORM convert_all_field_values CHANGING wa_EKKO.
	 
ENDLOOP.

  
*&---------------------------------------------------------------------*
*& Form convert_all_field_values
*&---------------------------------------------------------------------*
FORM convert_all_field_values CHANGING p_EKKO LIKE wa_EKKO.
DATA: ld_input(1000) TYPE c, ld_output(1000) TYPE C.
ENDFORM. 

*&---------------------------------------------------------------------*
*& Form process_as_string_field_values
*&---------------------------------------------------------------------*
FORM process_as_string_field_values CHANGING p_EKKO LIKE wa_EKKO.

TYPES: BEGIN OF T_CAT_C2NTB_STR, 
TABLE TYPE STRING,
KEYFLAG TYPE STRING,
FNAME TYPE STRING,
OFFSET TYPE STRING,
DDLEN TYPE STRING,
INTLEN TYPE STRING,
DECIMALS TYPE STRING,
DATATYPE TYPE STRING,
INTTYPE TYPE STRING,
FIELDTEXT TYPE STRING,END OF T_EKKO_STR.
DATA: WA_CAT_C2NTB_STR type T_EKKO_STR.

DATA: ld_text TYPE string.

LOOP AT IT_EKKO INTO WA_EKKO.
  MOVE-CORRESPONDING wa_EKKO TO WA_EKKO_STR.
  CONCATENATE: sy-vline
WA_CAT_C2NTB_STR-TABLE sy-vline 
WA_CAT_C2NTB_STR-KEYFLAG sy-vline 
WA_CAT_C2NTB_STR-FNAME sy-vline 
WA_CAT_C2NTB_STR-OFFSET sy-vline 
WA_CAT_C2NTB_STR-DDLEN sy-vline 
WA_CAT_C2NTB_STR-INTLEN sy-vline 
WA_CAT_C2NTB_STR-DECIMALS sy-vline 
WA_CAT_C2NTB_STR-DATATYPE sy-vline 
WA_CAT_C2NTB_STR-INTTYPE sy-vline 
WA_CAT_C2NTB_STR-FIELDTEXT sy-vline      INTO ld_text SEPARATED BY SPACE.

*Add any further fields from structure WA_EKKO_STR you want to CONCATENATE...
ENDLOOP.
ENDFORM.