Not sure what subject_title or postComment (is this the comment text?) has to do with anything since it seems like each blog entry has a unique numeric ID. (I assume that is what blog_entries_id and blog_id are)
A simple query might be:
Code:
select count(*) as bcount
from postreply
where blog_id=4
..obviously replacing 4 with the current blog_entries_id that you're counting for. The easiest way is to do this in two queries. One to fetch the date/subject/etc for the blog then another (similar to above) to count the comments.
-r