>>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 ==''
>

This won't work for text fields, you must trim them before comparing them.