[nycphp-talk] Building trees
Jim Hendricks(Biz Computing)
jim at bizcomputinginc.com
Wed Oct 16 16:16:28 EDT 2002
That's what I'm doing now, but in order to build the whole tree requires
multiple queries with this design. My latest idea is to add a tierlevel
field so I won't have to issue a query for parentID = 0 ( top level )
then iterate this result & generate a query for parentID = the id of the
row we are on in top level etc. right on down the line. If I have 4 top
level projects each with 3 sub projects and 1 of the subprojects have 2
subprojects this would require issuing 1 toplevel query, 4 2nd level
queries, 12 3rd level queries, and 2 4th level queries. All told for
this simple tree I will have issued 19 queries. If I have a tierlevel
I can issue 1 query per allowable tier which would be 4 queries in all
for a max 4 tierdepth tree. This would be the same no matter how many
items I have in the tree, nor how many children etc.
janis p gale wrote:
>or, if you were really lazy,
>you could just have a self-referencing table...
>
>tblObjects:
>objectID
>parentID
>fname
>lname
>etc...
>
>where parentID is the objectID of this object's parent
>
>what's nice about this is, you could query just one table
>to find all siblings -- just search for equivalent parentID's.
>similarly, it's easy to find orphans and objects that
>came before all others -- where parentID = NULL.
>
>
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