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Recursive field (Number of children)


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Hi,

 

Let say I want to create a blog in which user can add comments. Each comment can also be commented.

 

I want to create a field that calculates the total number of comments a blog or a comment has.

 

Here is the tables structure

 

Blogs (id, article, c_nbComments...)

Comments (id, id_blogid_parentComment, comment, c_nbComments, ...)

 

Let say I have two groups of Anchor-buoy

BL__BLOGS --< bl_COMMENTS

 

CMT__COMMENTS --< cmt_COMMENTS__children

 

So how can I calculate the total number of comments for each blog or comments?

 

Thanks

 

 

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In FM 12, you'd be able to whip up a SQL query in a case statement and have at it fairly easily. In FM 11, if your calculation is being stored in c_nbComments, do this:

 

In Blogs:

Count(bl_COMMENTS::id) + Sum(bl_COMMENTS::c_nbComments)

 

In Comments (evaluate this from the context of CMT_COMMENTS): 

Count(cmt_COMMENTS__children::id) + Sum(cmt_COMMENTS__children::c_nbComments)

 

That will give you the totals you want, though it might be a little slow if you're talking about very large numbers of nested comments

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D'uh... using the FM11 method I used sum twice instead of a count and a sum.

 

I am still looking at how to do it using SQL.

 

For the comments, I have tried something similar to this, but FM doesn't seem to be able to parse it.

WITH    q AS
(
	SELECT  id, id_parentComment
	FROM    CMT_COMMENTS
	UNION ALL
	SELECT  p.id, p.id_parentComment
	FROM    q
	JOIN    CMT_COMMENTS p
	ON      p.id = q.id_parentComment
)
SELECT  id, COUNT(*)
FROM    q
GROUP BY id
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