14.7. 集約関数

HQL のクエリはプロパティの集約関数の結果も返せます：

select avg(cat.weight), sum(cat.weight), max(cat.weight), count(cat)
from Cat cat

select avg(cat.weight), sum(cat.weight), max(cat.weight), count(cat)
from Cat cat

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サポートしている集約関数は以下のものです：

select 節において演算操作、連結と承認された SQL 関数を使うことができます:

select cat.weight + sum(kitten.weight)
from Cat cat
    join cat.kittens kitten
group by cat.id, cat.weight

select cat.weight + sum(kitten.weight)
from Cat cat
    join cat.kittens kitten
group by cat.id, cat.weight

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select firstName||' '||initial||' '||upper(lastName) from Person

select firstName||' '||initial||' '||upper(lastName) from Person

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SQL と同じ意味を持つ distinct と all キーワードを使うことができます。

select distinct cat.name from Cat cat

select count(distinct cat.name), count(cat) from Cat cat

select distinct cat.name from Cat cat

select count(distinct cat.name), count(cat) from Cat cat

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