On Wed, Jun 17, 2009 at 8:33 AM, Albe Laurenz<laurenz.a...@wien.gv.at> wrote:

>
> I don't understand your data model well enough to understand
> the query, so I can only give you general hints (which you probably
> already know):

He is effectively joining same table 4 times in a for loop, to get
result, this is veeery ineffective.
imagine:
for(x)
  for(x)
    for(x)
     for(x)
..

where X is number of rows in table matrix. not scarred yet ?

-- 
GJ

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