Regardaing secondary index

hi all,

i want to create the secondary index on mseg table.

here i am having select stament like this...

which fields can i select in the secondary index.

give me a brief explain.

SELECT MSEG~MBLNR

MSEG~BWART

MSEG~WERKS

MSEG~SHKZG

MSEG~MATNR

MSEG~ERFMG

MSEG~UMWRK

MKPF~MBLNR

MKPF~BUDAT

MSEG~XAUTO

MSEG~EBELN

INTO TABLE I_3MSEG

FROM MSEG

INNER JOIN MKPF

ON MSEG_{MBLNR = MKPF}MBLNR

WHERE MSEG~BWART IN ('301')

AND MSEG~MATNR IN S_MATNR

AND MSEG~WERKS IN S_SPLANT

AND MSEG~UMWRK IN S_RPLANT

AND MKPF~BUDAT IN S_AEDAT

AND MSEG~XAUTO <> 'X'

AND MSEG~EBELN IN S_EBELN.

Regards..

Anand.N