Mysql insert into/sum/union!

[Datenhamster]

Verwende zwar kein MySQL, aber ich mache das immer so, dass ich die zu verarbeitenden Daten für das Union minimiere:

insert into (
select .... sum(wertsum) from (
select ...,sum(wert1) as wertsum from ... where ... group by ...
UNION
select ...,sum(wert1) as wertsum from ... where ... group by ...
UNION
select ...,sum(wert1) as wertsum from ... where ... group by ...
)
)
group by ...