HQL with Null check for one-to-one relation

问题:

I have the following one-to-one relation in Hibernate (that could be null):

<one-to-one name="details" class="com.example.Details" lazy="false" cascade="all"/> 

I am trying to select all entities that have non-null details with HQL:

from Entity e where e.details is not null 

but this returns all entities, no matter whether details are null or not.

What would be a correct HQL then?

回答1:

Ok I found the solution:

select e from Entity e join e.details d where d is not null 

回答2:

Let's suppose this one-to-one relation is part of the mapping of herpderp table, hence herpderp entity has the details property.

Do you mean the query returns those herpderp records where the herpderp.details field is null?

Or do you mean something like this?

from Entity e where e.details.someDetailsField is not null 

回答3:

You can also most likely use the elements HQL function.

From the Expressions section of HQL 3.3 Documentation

from Cat cat where exists elements(cat.kittens) 

Which should translate to your query as

Select Entity e where exists elements(e.details) 

文章来源: HQL with Null check for one-to-one relation