How to filter null value in sql

Question

I have a situation in my sql statement. In this sql statement, I joined 3 tables together (Application_Detail, Teacher_Detail, and Class_Detail), and than I used WHERE to filter my table to find out how many teacher used this application, I found the following result.

As you can see in the 1st record, both teacher related and class related field are null. I am wondering is there a way to filter out the 1st record and only show the 2,3,4 record? because I want to only want to show the record if there are some value in teacherId, teacherName, class, or grade column.

   teacherId teacherName   applicationName  class   grade
1. NULL      NULL         Excel            NULL     NULL
2. 5         NULL         Excel            NULL     NULL
3. NULL      NULL         Excel            A        6
4  NULL      NULL         Excel            B        2 

Here is my SQL command

SELECT
   td.teacherId,
   teacherName,
   applicationName,
   class,
   grade
FROM
   [AppUser_Detail] as aud
LEFT OUTER JOIN [Teacher_Detail] as td ON aud.teacherId = td.teacherId
LEFT OUTER JOIN [Application_Detail] as ad ON aud.applicationId = ad.applicationId
LEFT OUTER JOIN [Class_Detail] as cd ON aud.classId = cd.classId
WHERE
aud.applicationId = 6 //I filter if my application Id is 6 

Answer 1

Try this:

SELECT
   td.teacherId,
   teacherName,
   applicationName,
   class,
   grade
FROM
   [AppUser_Detail] as aud
LEFT OUTER JOIN [Teacher_Detail] as td ON aud.teacherId = td.teacherId
LEFT OUTER JOIN [Application_Detail] as ad ON aud.applicationId = ad.applicationId
LEFT OUTER JOIN [Class_Detail] as cd ON aud.classId = cd.classId
WHERE
td.teacherId is not null OR class is not null OR grade is not null