Select query in case of Multiple line items

Hi Gurus ,

I've a doubt in general SQL select query. I want to know , if suppose I've an internal table - itab . I've fetched G/L Account numbers 1st, based on the input selections . Next , I want to loop on those G/L accounts. However, if the G/L account has multiple line items, then I personally use this select query -- >

loop at itab.
select <field> from <table> appending corresponding fields of  <itab1> where hkont eq itab-hkont.
endloop.

Now, the execution time for this query is longer than expected. The biggest problem here is, i've to sum up the totals as well. So totaling is an added load. I want to reduce the execution time of this. Kindly suggest me some good method in case u have any.

I've pasted the code which I've written , for u ppl to understand--

SELECT DISTINCT HKONT BELNR
  FROM BSIS
   INTO CORRESPONDING FIELDS OF TABLE OTAB
    WHERE HKONT IN S_RACCT
*      AND PRCTR IN P_PRCTR
      AND MONAT IN S_POPER
      AND BUKRS EQ P_BUKRS
      AND GJAHR EQ P_GJAHR
      AND PRCTR IN S_PRCTR.

***The code below takes a lot of time to execute.***
LOOP AT OTAB .

  SELECT DMBTR HKONT
  FROM BSIS APPENDING CORRESPONDING FIELDS OF TABLE CREDITS
    WHERE HKONT EQ OTAB-HKONT
      AND BELNR EQ OTAB-BELNR
      AND MONAT IN S_POPER
      AND BUKRS EQ P_BUKRS
      AND GJAHR EQ P_GJAHR
      AND PRCTR IN S_PRCTR
      AND SHKZG EQ 'H'.

  COLLECT CREDITS.

ENDLOOP.