Selection-Screen Parameter and select option

Question

Hi
I had a very small and silly problem , i have a selection screen in which i had one select-options and another parameter .
when i define both variable as select option i get output but if i define plant as parameter i dont get any output, .the code .
SELECTION-SCREEN : BEGIN OF BLOCK s_screen WITH  FRAME TITLE text-001.
SELECT-OPTIONS:   s_matnr FOR plaf-matnr.",       " OBLIGATORY,
PARAMETERS:       s_werks like plaf-pwwrk. "    ,  " OBLIGATORY.
SELECTION-SCREEN: END OF BLOCK s_screen.
in this code when
i enter material number i dont get output .
i enter plant the i get output
SELECT afko~aufnr
       afko~gamng
       afko~plnbez
       afpo~dwerk
       afpo~psmng
       afpo~matnr
       INTO CORRESPONDING FIELDS OF TABLE i_afko
       FROM afko INNER JOIN
       afpo ON afpoaufnr = afkoaufnr
       WHERE afpo~dwerk = s_werks
       and   afpo~matnr IN s_matnr
       AND   afpo~elikz = space.
regards
answers will be definately awarded points

Answer 1

Hi
When you use the plant in select-option, your code should be:
WHERE afpo~dwerk IN s_werks
      and afpo~matnr  IN s_matnr
if it's parameter:
WHERE afpo~dwerk = s_werks
       and afpo~matnr IN s_matnr
Are u sayng in the first case you get the data and in the second one you don't?
Max