如何檢查MySQL列以確保其包含值？

Question

我試圖從數據庫中選擇顯示='Y'並聲明！= null的所有行。 如何檢查列以確保其包含值？

 $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";

這既適合空白字段，又適合空字段。

Answer 2

announcement IS NOT NULL

要么

NOT ISNULL(announcement)