如何检查MySQL列以确保它包含值？

Question

我正在尝试从数据库中选择display ='Y'和announcement！= null的所有行。如何检查列以确保它包含值？

 $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";

这适用于空白字段和​​空字段。

Answer 2

announcement IS NOT NULL

或

NOT ISNULL(announcement)