Field symbols as Table name and in where condition in a select statement

Question

Hello All,
I have a scenario where I need to get user input on table name and old field value and new field value. Then based on user input, I need to select the record from the database. The column name for all the tables in question is different in the database, however there data type is the same and have same values.
I am not able to use a field symbol for comparing the old field value to fetch the relevant record in my where clause.
I cannnot loop through the entire table as it has 10 millilon records, please advice on how to add the where clause as field symbol as the table name is also dynamically assigned.
Here is my code:
DATA: TAB       LIKE SY-TNAME,
      TAB_COMP1 LIKE X031L-FIELDNAME,
      TAB_COMP2 LIKE X031L-FIELDNAME,
      NO_OF_FLD TYPE N.
DATA: BEGIN OF BUFFER,
        ALIGNMENT TYPE F,
        C(8000)   TYPE C,
      END OF BUFFER.
FIELD-SYMBOLS: <WA>   TYPE ANY,
              <COMP1> TYPE ANY,
              <COMP2> TYPE ANY.
GET TABLE NAME GIVEN BY USER IN LOCAL VARIABLE
  TAB = TAB_NAME.
CREATE FIELD NAME BASED ON THE TABLE NAME ENTERED.
  CASE TAB_NAME.
  WHEN 'OIUH_RV_GL'.
      KEY FIELD
        TAB_COMP1  = 'GL_GL_SYS_NO'.
        NO_OF_FLD  = 1.
  WHEN 'OIUH_RV_OPSL'.
      KEY FIELD
        TAB_COMP1  = 'OPSL_GL_SYS_NO'.
        NO_OF_FLD  = 1.
  WHEN 'OIUH_RV_OTAX'.
      NOT THE ONLY KEY FIELD
        TAB_COMP1  = 'OTAX_GL_SYS_NO'.
        TAB_COMP2  = 'OTAX_TAX_POS_NO'.
        NO_OF_FLD  = 2.
  WHEN 'OIUH_RV_GTAX'.
      NOT THE ONLY KEY FIELD
        TAB_COMP1  = 'GTAX_GL_SYS_NO'.
        TAB_COMP2  = 'GTAX_TAX_POS_NO'.
        NO_OF_FLD  = 2.
  WHEN OTHERS.
        EXIT.
  ENDCASE.
SET FIELD SYMBOL WITH APPROPRIATE TYPE TO BUFFER AREA.
ASSIGN BUFFER TO <WA> CASTING TYPE (TAB).
How to add where clause and remove the if condition in the select -- endselect
SELECT * FROM (TAB) INTO <WA>. 
  ASSIGN COMPONENT TAB_COMP1 OF STRUCTURE <WA> TO <COMP1>.
  IF NO_OF_FLD = 2.
    ASSIGN COMPONENT TAB_COMP2 OF STRUCTURE <WA> TO <COMP2>.
  ENDIF.
  IF <COMP1> = OLD_SYS_NO.
    code for updating table would come here
      WRITE: 'MATCH FOUND'.
      EXIT.
  ENDIF.
ENDSELECT.
Please advice. Thanks much.
Edited by: Shipra Jhunjhunwala on Jul 22, 2009 1:33 PM
Edited by: Shipra Jhunjhunwala on Jul 22, 2009 1:34 PM
Edited by: Shipra Jhunjhunwala on Jul 22, 2009 1:35 PM

Answer 1

1. Create single column table for holding field name depending on the table entered.
2. Take input from user: for e.g. table_name
3. Using case load single column table with required fields
   for e.g.
  CASE TAB_NAME.
   WHEN 'OIUH_RV_GL'.
         Append 'GL_GL_SYS_NO' to KEY_FIELD --> KEY_FIELD is the single line internal table as mentioned in step 1.
   WHEN 'OIUH_RV_OPSL'.
         Append 'OPSL_GL_SYS_NO'.
   WHEN 'OIUH_RV_OTAX'.
         Append 'OTAX_GL_SYS_NO' to KEY_FIELD.
           APPEND 'OTAX_TAX_POS_NO' to KEY_FIELD.
   WHEN 'OIUH_RV_GTAX'.
         Append 'GTAX_GL_SYS_NO' to KEY_FIELD.
           APPEND 'OTAX_TAX_POS_NO' to KEY_FIELD.
   WHEN OTHERS.
      EXIT.
   ENDCASE.
   Now depending on the table name you have required column ready
4. Create dynamic internal table using following sudo code
   Fill the fieldcatlog using the single column field table and DD03L table, See what all columns from DD03L you want to fill in field catlog table
   loop at internal table with all the fields.
    move it to field catalog.
    append field catalog.
   endloop.
5. Pass this field catalog table to static method create_dynamic_table method
   DATA table TYPE REF TO DATA. --> data object for holding handle to dynamic internal table.
   call method cl_alv_table_create=>create_dynamic_table
   exporting
      it_fieldcatalog = fieldcatalog_tab
   importing
      ep_table = table.
6. Now assign table reference to field symbol of type table.
   ASSIGN table->* to <field-tab>.
7. Also create work area <field-wa> using refrence of table.
   create data object wa LIKE LINE OF <field-tab>.
   ASSIGN wa->* to <field-wa>.
8. Also define field symbol for field name.
   for e.g. <field_name>
4. Dynamic internal table is ready
5. Now execute the select statement as follows:
   SELECT (KEY_FIELD)
     INTO <ITAB> --> created dynamically above
      FROM (TABLE_NAME)
     WHERE (WHERE).  --> WHERE is single line internal table having line type of CHAR72. So for every old value there will be one line
     Where condition is same as like we give in static way only difference in this case it will stored in internal table line wise.
    In this case you need to append all your where condition line by line in to WHERE.     
5. To fill this dynamic internal table using ASSIGN COMPONENT <Comp_number> OF STRUCTURE <field-wa> TO <field-name>
   So in this case if first field of structure STRUCT1 is user_id then sudo-code will be
   loop at internal table containing list of fields into field_wa --> single column field table
       ASSIGN COMPONENT field_wa OF STRUCTURE <field-wa> TO <field>. "Here field_wa is wa area for single column internal table holding all the fieldnames.
       Now <field-name> points to user_id field. Move some value into it as nornally we do with variables.
       Move <your_new_value> to <field-name>. --> Assign new value
        or
        <field-name> = <your_new_value>.
   Endloop.
6. After completing all the fields one row will be ready in <field_wa>.
   APPEND <field_wa> to <field_tab>.
Hope this helps you.
Thanks,
Augustin.