Hi-
I'm suffering from a performance problem, but when I look at my query, I'm not convinced that there isn't a better way to handle this in SQL. -So I'm seeking advice here before I go to the performance list.
I have three tables- case, actor and actor_case_assignment.
As the names imply, actor_case_assignment contains records that assign an actor to a case. Actors such as attorneys or judges may have many cases, while the average actor (we hope) only has one.
What I'm trying to do is link these tables to get back a single row per actor that shows the actor's name, the number of cases that actor is assigned to, and if they only have one case, I want the number for that case. This means I have to do some grouping to get the case count, but I'm then forced to use an aggregate function like max on the other fields. I hope there's a better way. Any suggestions?
Here's what I'm using right now:
select actor.actor_id, max(actor.actor_full_name), max(case_data.case_public_id), max(case_data.case_id), count(case_data.case_id) as case_count from actor, actor_case_assignment, case_data where actor.actor_full_name_uppercase like upper('martin%') and actor.actor_id = actor_case_assignment.actor_id and case_data.case_id = actor_case_assignment.case_id group by actor.actor_id order by max(actor.actor_full_name), case_count desc, limit 1000;
Thanks! -Nick
--------------------------------------------------------------------- Nick Fankhauser
[EMAIL PROTECTED] Phone 1.765.965.7363 Fax 1.765.962.9788 doxpop - Court records at your fingertips - http://www.doxpop.com/
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select count(as.case_id) as case_count, max(as.case_id) as max_case_id, a.actor_full_name from actors a, actor_case_assignment as where a.case_id = actor_case_assignment.case_id and a.actor_full_name_uppercase like upper('martin%') -- this field is(should be) indexed group by a.actor_full_name order by a.actor_full_name_uppercase -- this field is(should be) indexed
This query will not pick up any actors that a NOT assigned to a case, but you said in your criteria that all actors are assigned to at least one case. This query relys on that assumption and eliminates the expense of an outer join.
Also, you are always getting max_case_id but it is obvious that this will be the relevent case where case_count == 1 you can simply ignore max_case_id when case_count != 1
try running this query with explain to compare against the others.
Also, try adding an index to the actor_full_name_uppercase column since you are using it in an order by clause and searching on it. indexes will incur slight performance expenses when inserting and updating.
cheers.
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