uu=# explain analyze
uu-# select lower(substr(p.last_name,1,1)) as letter, count(*)
uu-# FROM course c join group_data gd on (c.active_group_id = gd.this_group_id)
uu-# join person p on (gd.item_text = p.userid)
uu-# join dyn_field_person dfp on (dfp.extern_item_id = 10 and dfp.giver=c.giver)
uu-# join dyn_field_content_person dfcp on (dfp.id = dfcp.dyn_field_id and dfcp.userid=p.userid)
uu-# left outer join participant pt on (pt.userid = p.userid and pt.course_id = 707)
uu-# WHERE c.id = 707
uu-# group by 1
uu-# ;
Why are you using this form of join ? When and if is not necessary use the implicit form.
Regards Gaetano Mendola
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