Use the aggregated functions in sap abap

C4A = '000'.             
SELECT * FROM T100       
 WHERE SPRSL = 'D' AND  
       ARBGB = '00'.    
 CHECK: T100-MSGNR > C4A.
 C4A = T100-MSGNR.      
ENDSELECT.               

SELECT MAX( MSGNR ) FROM T100 INTO C4A
WHERE SPRSL = 'D' AND               
      ARBGB = '00'.