Runtime Errors DBIF_RSQL_INVALID_RSQL

Hi

Runtime Errors         DBIF_RSQL_INVALID_RSQL

Except.                CX_SY_OPEN_SQL_DB

When I am hitting query as follows : -

SELECT MBLNR

             USNAM

       FROM MKPF

       INTO TABLE IT_MKPF

       WHERE MBLNR IN S_MBLNR.