Sql查询tbl注释

Question

Comment:tbl

CommentId PK  
CommentEntry  
CommentDate  
Category  
CommentCommentId  
BlogEntryId FK


Insert into Comment(CommentId, CommentEntry, CommentDate, Category, CommentCommentId, BlogEntryId)
Values("1","I love shoes","10-3-2011","1","" ,"13"),
("2","I love shoes too","10-4-2011","1","1" ,"13"),
("3","There nice shoes in the mall","2","","13");

问:对于给定博客条目上的第一条评论，只对该原始评论产生任何进一步的评论。应该提示用户输入博客条目的唯一标识符。

ANS应该是：

("1","I love shoes","10-3-2011","1","" ,"13"),
("2","I love shoes too","10-4-2011","1","1" ,"13")

请帮助了解sql

我想要做一个自我连接，接受BlogEntryId和产品第一个评论'CommentCommentId=""‘和第一个评论上的所有评论。

有关sql的帮助：)

Answer 1

只需在原始查询中添加一点：

SELECT * 
FROM Comment 
WHERE BlogEntryId = [?Blog Entry] 
AND (
    CommentId = (SELECT CommentId FROM Comment WHERE CommentDate = (SELECT min(CommentDate) from Comment))
    OR
    CommentCommentId = (SELECT CommentId FROM Comment WHERE CommentDate = (SELECT min(CommentDate) from Comment))
    )

Answer 2

我猜你想要这样的东西：

select * 
from comment c
join comment subc on c.commentcommentid = subc.commentid
where c.commentid = @inputID

这是一个自连接。

我认为家庭作业问题的答案很简单：

select *
from comment
where commentcommentid = @inputid