谁能告诉我这个SQL语句的意思？小菜先谢谢各位了

delete tbTopic where TopicBoardID in (select BoardID from tbBoard where BoardClassID=@ClassID);

从表中删除 TopicBoardID属于括号里查询出来的结果
delete tbBoard where BoardClassID=@ClassID;
delete tbClass where ClassID=@ClassID

删除ClassID=@ClassID的资料栏

三个删除语句，其中有各变量是@ClassID

可能是存储过程的参数

delete tbTopic where TopicBoardID in (select BoardID from tbBoard where BoardClassID=@ClassID);

生成一个满足条件的集合select BoardID from tbBoard where BoardClassID=@ClassID
删除在上面的集合中的纪录
delete tbTopic where TopicBoardID in。。。

。。。