SELECT时候，如何跳过带有空值字段的数据项？

以下是我的php代码：，

$sql = "SELECT author,tags,subject,tid,authorid,dateline,fid FROM threads ORDER BY dateline DESC LIMIT 10"

如果tags是空值，则跳过，该怎么改呢？

回复内容：

以下是我的php代码：，

$sql = "SELECT author,tags,subject,tid,authorid,dateline,fid FROM threads ORDER BY dateline DESC LIMIT 10"

如果tags是空值，则跳过，该怎么改呢？

如果空值是:NULL
则：

$sql = "SELECT author,tags,subject,tid,authorid,dateline,fid FROM threads WHERE tags IS NOT NULL ORDER BY dateline DESC LIMIT 10"

如果空值是:''

$sql = "SELECT author,tags,subject,tid,authorid,dateline,fid FROM threads WHERE tags !='' ORDER BY dateline DESC LIMIT 10"