I have fixed the issue now. I am using

SELECT (parent_author + '/' +  parent_permlink), COUNT((parent_author + '/' +  parent_permlink)) FROM [dbo].[Comments] 
where author = 'steemladder' 
 AND created >= DATEADD(day,-1, GETDATE())
 GROUP BY (parent_author + '/' +  parent_permlink);

To track the number of comments on a post and I am getting only one comment. I will monitor it for couple more days.