ABAP Select data from SAP table LISSYSTEM into internal table

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

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

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

*Select data and declare internal table using in-line method @DATA
*SELECT *
*  FROM LISSYSTEM
*  INTO TABLE @DATA(IT_LISSYSTEM2).
*--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_LISSYSTEM INDEX 1 INTO DATA(WA_LISSYSTEM2).


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

*To update a field value using a field symbol simply change the value via the field symbol pointer
<LISSYSTEM>-DOMNAM = 1.
<LISSYSTEM>-SYSNAM = 1.
<LISSYSTEM>-STATE = 1.
<LISSYSTEM>-SYSTYPE = 1.
<LISSYSTEM>-SYSROLE = 1.

ENDLOOP.

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

*Write selected data to screen/report before conversion.
  WRITE:/ sy-vline,   WA_LISSYSTEM-TMSUNISRV, sy-vline,
  WA_LISSYSTEM-LISPLUGIN, sy-vline,
  WA_LISSYSTEM-LISMANAGER, sy-vline,
ENDLOOP.
   
*Add any further fields from structure WA_LISSYSTEM 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_LISSYSTEM 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_LISSYSTEM INTO WA_LISSYSTEM.


*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_LISSYSTEM_STR, 
DOMNAM TYPE STRING,
SYSNAM TYPE STRING,
STATE TYPE STRING,
SYSTYPE TYPE STRING,
SYSROLE TYPE STRING,
TMSUNISRV TYPE STRING,
LISPLUGIN TYPE STRING,
LISMANAGER TYPE STRING,END OF T_EKKO_STR.
DATA: WA_LISSYSTEM_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_LISSYSTEM_STR-DOMNAM sy-vline 
WA_LISSYSTEM_STR-SYSNAM sy-vline 
WA_LISSYSTEM_STR-STATE sy-vline 
WA_LISSYSTEM_STR-SYSTYPE sy-vline 
WA_LISSYSTEM_STR-SYSROLE sy-vline 
WA_LISSYSTEM_STR-TMSUNISRV sy-vline 
WA_LISSYSTEM_STR-LISPLUGIN sy-vline 
WA_LISSYSTEM_STR-LISMANAGER sy-vline      INTO ld_text SEPARATED BY SPACE.

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