How to enhance the following query?

Question

Hi all,
          I am using the following piece of code to some fields from table STAS.However this query is taking a long time to execute.
Can anyone please tell me how can i enhance it so that it may execute faster?Thnx in advance.
LOOP AT IT_FG WHERE STLAL = ' '.                                   
  SELECT STLAL FROM STAS
  INTO IT_FG-STLAL
  WHERE STLNR = IT_FG-STLNR
    AND STLKN = IT_FG-STLKN.                                         
  MODIFY IT_FG.                                                    
  ENDSELECT.                                                       
ENDLOOP.
Regards,
S.choudhury.
Edited by: Rob Burbank on Dec 23, 2009 12:02 PM

Answer 1

The above recommendation are only o.k., if you use sorted tables. However, maybe people don't mention because you should always use sorted tables. I am joking, but the recommendation is true!
Otherwise use binary search, but better use sorted tables!
And for the loop you should use ASSIGNING which speeds up the modify.
field-symbols: <fs>   type it_fg.
SELECT STLAL STLNR STLKN
              INTO table IT_new
              FROM STAS
              for all entries in  IT_FG
              WHERE STLNR = IT_FG-STLNR
              AND STLKN = IT_FG-STLKN.
SORT it_new BY stlnr stlkn.
LOOP AT IT_FG ASSIGNING <fs>
          WHERE STLAL = ' '.
     read table  IT_new 
             into wa_new
             WITH KEY STLNR = IT_FG-STLNR
              AND STLKN         = IT_FG-STLKN
             BINARY SEARCH.
* type ???.
      <fs> = wa_new-STLAL.
ENDLOOP.