How do I check a MySQL column to make sure it contains a value?

Question

I am trying to select all rows from a database where display = 'Y' and announcement != null. How can I check a column to make sure it contains a value?

 $qry = "select * 
         from  school
  where  display='Y'
  order by name, announcement, last_update";

Answer 1

$qry = "select *       
         from   school
         where  display='Y'
         and (announcement != '' AND announcement IS NOT null)
         order by name, announcement, last_update";

This caters for blank fields as well as null fields.

Answer 2

announcement IS NOT NULL

or

NOT ISNULL(announcement)