INSERT NULL TI DATETIMR FILED

Question

I TRIED TO INSERT NULL INTO DATETIME FILED , ATTHE TIME ERROR MESSAGE  IS DATE PARAMETER VALUE NOT SUPPLIED,



THIS CASE RISES WHEN MORE FILEDS IN THE TABLE,INCLUDES DATEFILED

.....
 I GIVES QUERY ""INSERT INTO TMPTABLE VALUES(1,266,NULL)"

..........


NOT GOT ERROR WHEN DIRECT EXCUTE ONLY DATE FILED WITH NULL,AT THE TIME IT WILL SUCCESS,,,,
LIKE THIS "INSERT INTO TMPTABLE(BACKDATE) VALUES(NULL)"