For each billing Document created in the system, following tables will have the data. Following select statement showing how to connect the BSIS and BSEG .
IF L_RELOAD_DATA = 'X'.
SELECT BUKRS HKONT ZUONR gjahr BELNR BUZEI bschl wrbtr dmbtr SHKZG FROM BSIS INTO TABLE IT_BSIS
WHERE BUKRS = <FIELD4> AND
HKONT in r_HKONT AND
ZUONR = KOMP-VGBEL.
SORT IT_BSIS .
* Now Read the data from the BSEG using the above Accounting Docs and Item/Posting key
if not it_bsis[] is initial.
select bukrs belnr buzei bschl zuonr vbel2 posn2 hkont dmbtr into table it_bseg
from bseg for all entries in it_bsis
where bukrs = it_bsis-bukrs and
belnr = it_bsis-belnr and
gjahr = it_bsis-gjahr and
BUZEI = it_bsis-BUZEI.
endif.