ABAP Select data from SAP table MDC_FIELD_SPECIFICATION into internal table

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Below is a number of ABAP code snippets to demonstrate how to select data from SAP MDC_FIELD_SPECIFICATION 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 MDC_FIELD_SPECIFICATION. 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 MDC_FIELD_SPECIFICATION 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_MDC_FIELD_SPECIFICATION TYPE STANDARD TABLE OF MDC_FIELD_SPECIFICATION,
      WA_MDC_FIELD_SPECIFICATION TYPE MDC_FIELD_SPECIFICATION,
      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: <MDC_FIELD_SPECIFICATION> TYPE MDC_FIELD_SPECIFICATION.

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

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

*Select data and declare internal table using in-line method @DATA
*SELECT *
*  FROM MDC_FIELD_SPECIFICATION
*  INTO TABLE @DATA(IT_MDC_FIELD_SPECIFICATION2).
*--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_MDC_FIELD_SPECIFICATION INDEX 1 INTO DATA(WA_MDC_FIELD_SPECIFICATION2).


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

*To update a field value using a field symbol simply change the value via the field symbol pointer
<MDC_FIELD_SPECIFICATION>-FIELD_NAME = 1.
<MDC_FIELD_SPECIFICATION>-TYPE_NAME = 1.
<MDC_FIELD_SPECIFICATION>-LENGTH = 1.
<MDC_FIELD_SPECIFICATION>-DECIMALS = 1.
<MDC_FIELD_SPECIFICATION>-CASE_SENSITIVE = 1.

ENDLOOP.

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

*Write selected data to screen/report before conversion.
  WRITE:/ sy-vline,   WA_MDC_FIELD_SPECIFICATION-TECHNICAL, sy-vline,
  WA_MDC_FIELD_SPECIFICATION-IMMUTABLE, sy-vline,
  WA_MDC_FIELD_SPECIFICATION-SELECTIVE, sy-vline,
  WA_MDC_FIELD_SPECIFICATION-OBSCURED, sy-vline,
ENDLOOP.
   
*Add any further fields from structure WA_MDC_FIELD_SPECIFICATION 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_MDC_FIELD_SPECIFICATION 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_MDC_FIELD_SPECIFICATION INTO WA_MDC_FIELD_SPECIFICATION.


*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_MDC_FIELD_SPECIFICATION_STR, 
FIELD_NAME TYPE STRING,
TYPE_NAME TYPE STRING,
LENGTH TYPE STRING,
DECIMALS TYPE STRING,
CASE_SENSITIVE TYPE STRING,
TECHNICAL TYPE STRING,
IMMUTABLE TYPE STRING,
SELECTIVE TYPE STRING,
OBSCURED TYPE STRING,END OF T_EKKO_STR.
DATA: WA_MDC_FIELD_SPECIFICATION_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_MDC_FIELD_SPECIFICATION_STR-FIELD_NAME sy-vline 
WA_MDC_FIELD_SPECIFICATION_STR-TYPE_NAME sy-vline 
WA_MDC_FIELD_SPECIFICATION_STR-LENGTH sy-vline 
WA_MDC_FIELD_SPECIFICATION_STR-DECIMALS sy-vline 
WA_MDC_FIELD_SPECIFICATION_STR-CASE_SENSITIVE sy-vline 
WA_MDC_FIELD_SPECIFICATION_STR-TECHNICAL sy-vline 
WA_MDC_FIELD_SPECIFICATION_STR-IMMUTABLE sy-vline 
WA_MDC_FIELD_SPECIFICATION_STR-SELECTIVE sy-vline 
WA_MDC_FIELD_SPECIFICATION_STR-OBSCURED sy-vline      INTO ld_text SEPARATED BY SPACE.

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