How to get Entity Items by grouping by associations CAP CDS?

[former_member498613]

This is my data-model.cds:

    entity Authors : {
      key ID : UUID;
      name : String(111);
      books : Association to many Books on books.author = $self;
    }

    entity Books : {
      key ID : UUID;
      author : Association to Authors;
      title : String;
}

How can i get JSON with oData query to group all books under each author?

So for example for author "John Doe" i will get all related books and for "Emily" all of her books?
Heres the wanted result:

{
"John Doe": [
{id:1,title: "first book"},
{id:2,title: "second book"}
],
"Emily ": [
{id:3,title: "Harrry poter"},
{id:4,title: "second Harrry"}
]
}

[pierre_dominique2 · Accepted solution]

You can use the $expand parameter for this: Serving OData APIs

EDIT: add link to the documentation

[former_member498613 · Accepted solution]

Works Great!
heres the url that i'v needed:
<service>admin/Authors?$expand=books($select=ID,title)