如何检查MySQL列以确保它包含值？

Question

我想从数据库中选择display ='Y'和公告！= null的所有行。我如何检查一列以确保它包含一个值？

$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"; 

这迎合了空白领域以及空字段。

Answer 2

announcement IS NOT NULL 

或

NOT ISNULL(announcement)