CODEWITHSUNDEEP
sqlt-sql
Christian Rios
Christian Rios

Reputation: 477

Sorting comments with nested replies

I am trying to come up with a query that will return comments following their replies and its replies.

Something like 

comment 1
reply 1.1
reply 1.1.1
reply 1.2
comment 2
comment 3
comment 3.1

etc

I have this so far

SELECT [CommentID]
  ,[ParentID]
  ,[Message]
  , ROW_NUMBER() over(partition by ParentID order by CommentID ) as rn
  ,[CreatedBy]
  ,[CreatedDate]
  FROM [DBNAME].[dbo].[Commenttable] 
  GROUP BY [CommentID],[ParentID],[CreatedDate],[Message],[CreatedBy]

but what I get is 

comment 1
comment 2
comment 3
reply 1.1
reply 1.2
reply 3.1
reply 1.1.1

Basic Structure is just a table with Comment ID, Parent ID, and the message. The comments and replies are just to help explain what I am trying to achieve

Upvotes: 1

Views: 1070

Answers (1)

HABO
HABO

Reputation: 15816

Give this a try:

declare @CommentTable as Table ( CommentId Int Identity, ParentId Int Null, Message VarChar(16) )
insert into @CommentTable ( ParentId, Message ) values
  ( null, '1' ),
  ( null, '2' ), ( 1, '1.1' ),
  ( null, '3' ), ( 4, '3.1' ), ( 3, '1.1.1' ), ( 1, '1.2' )
select * from @CommentTable

; with Cindy as (
  -- Start with the base comments.
  select CommentId, ParentId, Message, Row_Number() over ( order by CommentId ) as Number,
    Cast( Row_Number() over ( order by CommentId ) as VarChar(1000) ) as Path,
    Cast( Right( '0000' + Cast( Row_Number() over ( order by CommentId ) as VarChar(4) ), 5 ) as VarChar(1000) ) as OrderPath
    from @CommentTable
    where ParentId is NULL
  union all
  -- Add replies on layer at a time.
  select CT.CommentId, CT.ParentId, CT.Message, Row_Number() over ( order by CT.CommentId ),
    Cast( C.Path + '.' + Cast( Row_Number() over ( order by CT.CommentId ) as VarChar(4) ) as VarChar(1000) ),
    Cast( C.OrderPath + Right( '0000' + Cast( Row_Number() over ( order by CT.CommentId ) as VarChar(4) ), 5 ) as VarChar(1000) )
    from @CommentTable as CT inner join
      Cindy as C on C.CommentId = CT.ParentId
  )
  select *
    from Cindy
    order by OrderPath

Upvotes: 3

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