删除记录在SQL Server上的外键

Question

我有3个表：

• 后
• 像表之间
• 评论

关系是：

• 邮寄表格：postid PK
• 如表：LikeID PK，帖子ID FK，CommentID FK
• 评语表：CommentID PK，帖子ID FK，CommentReplybyID FK（自连接上commentid）

现在我要删除帖子表，但我交我得到一个错误。

我使用下面这个查询：

begin tran 

declare @userid int = 68; 
declare @postid int = 15; 

delete from likes 
where postid = @postid and userid = @userid 

delete from comments 
where postid = @postid and userid = @userid 

delete from post 
where postid = @postid and userid = @userid 

rollback tran 

我得到这些错误：

消息547，级别16，状态0，第8行
DELETE语句冲突以相同的表REFERENCE约束“Comments_fk3”。冲突发生在数据库“development-topthat”，表“dbo.Comments”，列'CommentReplyID'。

Msg 547，Level 16，State 0，Line 9
DELETE语句与REFERENCE约束“Likes_fk1”冲突。冲突发生在数据库“development-topthat”，表“dbo.Likes”，列'PostID'。

我需要帮助，我在哪里做错了。如何实现这一目标？

Answer 1

通过CommentReplyID的外观和自我连接评论我怀疑你在评论表中有某种嵌套关系。

您需要删除CommentReplyId与删除注释相匹配的记录。

begin tran 

declare @userid int = 68; 
declare @postid int = 15; 

-- are you sure userid should be used here? 
delete from likes where postid = @postid and userid = @userid 

delete from comments c1 join comments c2 on c2.CommentReplyId = c1.CommentId where c1.postid = @postid and c1.userid = @userid 

delete from comments where postid =@postid and userid = @userid 

delete from post where postid = @postid and userid = @userid 

rollback tran