An internal table icode contains the following entries: Field1 Field2 -------------- John 12345 Alice 23478 Sam 54321 john 50000 DATA: BEGIN OF ICODE OCCURS 0, FIELD1(5), FIELD2(5), END OF ICODE. READ TABLE ICODE WITH KEY FIELD1 = 'John' BINARY SEARCH. Why does executing the above code return a sy-subrc of 4?