>I have student.dbf with fileds 1.regno(C), 2.name(C), 3.dob(D), 4.Course(C), 5.category(C)
>
>How to write SQL Query for find empty value of all field of my "student.dbf" table?

Try

select * from Student ;
WHERE RegNo=='' ;
OR Name == '' ;
OR DOB = {} ;
OR Course =='';
OR Category ==''