Delete from table where col is null;

这样写不行，删除不掉；

The DELETE FROM statement is used delete rows from a database table.

DELETE FROM语句是用来从数据库表中删除记录行的。

I think it is preventing the delete from working in the way you want.

我认为这是防止删除按你想要的方式工作。

If you delete from the collection, the clip can still be found in Unclassified Clips.

如果从收藏集中删除剪辑，还可以在“未分类的剪辑”中找到该剪辑。