Обсуждение: aggregates of aggregates
Does anyone know of any plans to support aggregates of aggregates in the future? It would be great to be able to select with an aggregate function from another select statement with another aggregate function. I have tried putting the result of an aggregate function in a view and then performing another aggregate function on the view, but I get the error that nested aggregates are not supported. My solution was to put the result of the first aggregate function in a temp table, then doing the other select statement on the temp table. This is not very efficient as the temp table can have up to a million records in it. Is this feature planned for Postgres? Does anyone know a better workaround than the way I am doing it? Thanks in advance, -Tor
Tor Roberts <pg@econsci.net> writes: > Does anyone know of any plans to support aggregates of aggregates in the > future? Not directly: it makes no sense in the SQL semantic model. We do have plans to support subselect-in-FROM (hopefully in 7.2), which would allow constructs like SELECT count(*) FROM (SELECT foo,count(*) FROM bar GROUP BY foo) The same revisions will also be needed before views that involve grouping or aggregates will work right in all but the simplest cases. > My solution was to put the result of the first aggregate function in a > temp table, then doing the other select statement on the temp table. This > is not very efficient as the temp table can have up to a million records > in it. Sounds like a good workaround for now. regards, tom lane