14.13. 子查询

对于支持子查询的数据库,Hibernate支持在查询中使用子查询。一个子查询必须被圆括号包围起来(经常是SQL聚集函数的圆括号)。 甚至相互关联的子查询(引用到外部查询中的别名的子查询)也是允许的。

from Cat as fatcat
where fatcat.weight > (
    select avg(cat.weight) from DomesticCat cat
)
from DomesticCat as cat
where cat.name = some (
    select name.nickName from Name as name
)
from Cat as cat
where not exists (
    from Cat as mate where mate.mate = cat
)
from DomesticCat as cat
where cat.name not in (
    select name.nickName from Name as name
)
select cat.id, (select max(kit.weight) from cat.kitten kit)
from Cat as cat

注意,HQL自查询只可以在select或者where子句中出现。

Note that subqueries can also utilize row value constructor syntax. See 第 14.18 节 “Row value constructor syntax” for more details.