Wrongly I put the Sy-subrc in above code.
Please refer below code.
LOOP AT LT/Rab/KPI_HEAD INTO GWA_/Rab/KPI_HEAD.
loop at LT/Rab/KPI_MAPP INTO GWA_/Rab/KPI_MAPP.
if GWA_/Rab/KPI_MAPP-XX100009 CS GWA_/Rab/KPI_HEAD-XX100012.
WRITE: ' no selection ID found in table'.
ENDLOOP.
endloop