Create Open SQL query dynamically out of custom table

Open SQL offers really flexible way of use. In below example you can see dynamically created query, there is not clear from the beginning what we are looking for, from which table and under what WHERE condition. The example shows how to get data for a certain user based on another custom table storing target table name and expected field name for username. That's all. The rest is a dynamic miracle :)

Fully flexible query:

    SELECT SINGLE (<fs_user_table>-fieldname) FROM (<fs_user_table>-tabname)
    INTO gv_text
    WHERE (gt_sql_where).


Note: Even target INTO variable can be created dynamically - see another post.

Source table for Query

Structure of custom table Z_USER_TABS:

Possible table content (user related tables):

ABAP coding:

REPORT z_osql_dynamics.

PARAMETER p_user TYPE xubname.

" Get/List user param table list
TYPES: BEGIN OF tys_user_tab,
        tabname   TYPE tabname,
        fieldname TYPE fieldname,
       END OF tys_user_tab.

TYPES tyv_user_tab TYPE c LENGTH 72.

DATA: gt_user_tables TYPE STANDARD TABLE OF tys_user_tab,
      gt_sql_where   TYPE STANDARD TABLE OF tyv_user_tab,
      gv_sql_where   LIKE LINE OF gt_sql_where,
      gv_text        TYPE string.


START-OF-SELECTION.

  " Get list of all user param tables to be checked
  SELECT tabname fieldname
  FROM z_user_tabs
  INTO TABLE gt_user_tables.

  FIELD-SYMBOLS <fs_user_table> LIKE LINE OF gt_user_tables.
  LOOP AT gt_user_tables ASSIGNING <fs_user_table>.

    CLEAR gv_sql_where.
    CLEAR gt_sql_where.

    CONCATENATE <fs_user_table>-fieldname ' = ' '`' p_user '`' INTO gv_sql_where RESPECTING BLANKS.
    APPEND gv_sql_where TO gt_sql_where.

    SELECT SINGLE (<fs_user_table>-fieldname) FROM (<fs_user_table>-tabname)
    INTO gv_text
    WHERE (gt_sql_where).
    IF sy-subrc = 0.
      WRITE: / <fs_user_table>-tabname, <fs_user_table>-fieldname, ' = ', gv_text.
    ENDIF.
  ENDLOOP.

END-OF-SELECTION.