Hi all,
I have this query:
select CATALOGUES.idcatalogue, CATALOGUES.type, PERSONS.surname,
max(HISTORY.startingfrom) as maxdate
FROM PERSONS
INNER JOIN CATALOGUES
ON CATALOGUES.idperson = PERSONS.idperson
INNER JOIN HISTORY
ON HISTORY.idcatalogue = CATALOGUES.idcatalogue
WHERE CATALOGUES.active='y'
group by PERSON.surname, CATALOGUES.idcatalogue, CATALOGUES.type
with indexes on:
PERSONS.surname
PERSONS.idperson
CATALOGUES.active
CATALOGUES.idcatalogue
CATALOGUES.type
HISTORY.idcatalogue
HISTORY.startingfrom
Tables contains about:
PERSONS 700000 records
CATALOGUES 70 records
HISTORY 4 million records
My query is extremely slow (about 90 seconds).
If I exclude the group by and the max functions, it is extremely fast.
So problem should be in group by.
How can I improve the performance?
Thank you very much for your explanation.
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