# Return structured results from queries · Your first Rell app on Chromia · Learn Chromia > Queries often need to return data assembled from more than one entity, such as a book together with its reviews. You can shape that result with a struct, so… Source: https://chromia.com/learn/book-review/input-verification/structure/ Your first Rell app on ChromiaLesson 14 of 26 1. [01Your first Rell app on Chromia](https://chromia.com/learn/book-review/introduction/) 2. [02Set up your project](https://chromia.com/learn/book-review/setup/) 3. [03Rell project structure](https://chromia.com/learn/book-review/rell-structure/) Part 1: Define your first entity 1. [04Overview](https://chromia.com/learn/book-review/book-entity/) 2. [05Create your first entity](https://chromia.com/learn/book-review/book-entity/tables/) 3. [06Add your first operation](https://chromia.com/learn/book-review/book-entity/basic-operations/) 4. [07Query every book](https://chromia.com/learn/book-review/book-entity/write-queries/) Part 2: Add a related entity 1. [08Overview](https://chromia.com/learn/book-review/book-review-entity/) 2. [09Define the book review entity](https://chromia.com/learn/book-review/book-review-entity/tables/) 3. [10Add an operation for creating book reviews](https://chromia.com/learn/book-review/book-review-entity/basic-operations/) 4. [11Query all reviews for a book](https://chromia.com/learn/book-review/book-review-entity/write-queries/) Part 3: Checking and validating inputs 1. [12Overview](https://chromia.com/learn/book-review/input-verification/) 2. [13Verify inputs](https://chromia.com/learn/book-review/input-verification/input-verification/) 3. [14Return structured results from queries](https://chromia.com/learn/book-review/input-verification/structure/) Part 4: Signing transactions and filtering queries 1. [15Overview](https://chromia.com/learn/book-review/sign-transaction/) 2. [16Sign a transaction](https://chromia.com/learn/book-review/sign-transaction/sign-transaction/) 3. [17Filter and sort query results](https://chromia.com/learn/book-review/sign-transaction/structure/) Part 5: Blockchain state and transactions explained 1. [18Overview](https://chromia.com/learn/book-review/blockchain-transactions/) 2. [19How blockchain state and transactions work](https://chromia.com/learn/book-review/blockchain-transactions/query-transaction/) 3. [20Walking through an example](https://chromia.com/learn/book-review/blockchain-transactions/example/) Part 6: Create the client 1. [21Overview](https://chromia.com/learn/book-review/build-client/) 2. [22Prerequisites](https://chromia.com/learn/book-review/build-client/prerequisites/) 3. [23Establishing a connection to Chromia](https://chromia.com/learn/book-review/build-client/sign-transaction/) 4. [24Query the blockchain using postchain-client](https://chromia.com/learn/book-review/build-client/query-blockchain/) 5. [25Complete the example](https://chromia.com/learn/book-review/build-client/complete-example/) 1. [26What’s next?](https://chromia.com/learn/book-review/what-next/) [Learn](https://chromia.com/learn/)[Your first Rell app on Chromia](https://chromia.com/learn/book-review/) 14 / 26Part 3: Checking and validating inputsBeginner # Return structured results from queries Queries often need to return data assembled from more than one entity, such as a book together with its reviews. You can shape that result with a struct, so the client receives a single, well-defined object instead of loose values. You will define a `book_review_dto` struct that holds both the book details and the review details, and then change the query so it returns that struct. ### Define the struct Data structures like this belong in `src/main/entities.rell`. The new `book_review_dto` struct carries the book information alongside the review fields. Add the following code to `src/main/entities.rell`: src/main/entities.rell ``` struct book_review_dto { book: struct; reviewer_name: text; review: text; rating: integer; } ``` A field of type `struct` holds every field of the referenced `book` entity. Using it in an expression causes an implicit join that loads those fields. ### Update the query Now change `get_all_reviews_for_book` so it returns `book_review_dto` values. Each result then contains the book and the review together. Replace the query in `src/main/queries.rell` with this version: src/main/queries.rell ``` query get_all_reviews_for_book(isbn: text) { require(book @? { .isbn == isbn }, "Book with isbn %s not found".format(isbn)); val reviews = book_review @* { .book.isbn == isbn } ( book_review_dto( book = .book.to_struct(), .reviewer_name, .review, .rating ) ); return reviews; } ``` ### Explanation 1. **Struct definition:** `book_review_dto` groups the book and review details into one value, so related data travels as a unit. 2. **Updated query:** * `require` verifies that a book with the given ISBN exists. * `book_review @* { .book.isbn == isbn }` selects every review for that book. * The struct's `book` attribute is filled with `book_review.book.to_struct()`, which turns the entity reference into a struct value. This is what causes the implicit join that loads all fields of the referenced `book` entity. ### Testing the update Verify the change with the following steps: 1. **Update the node:** With a Chromia node already running, push the latest version of your dapp to it: shell ```nolines chr node update ``` Otherwise, start the node with: shell ```nolines chr node start ``` note Updating a running node does not take effect instantly. The new code may only become active once the next block is produced. 2. **Run the query:** Call the query from the Chromia CLI: shell ```nolines chr query get_all_reviews_for_book "isbn=ISBN1234" ``` You should see output similar to this: json ``` [ { "book": { "author": "George Orwell", "isbn": "ISBN1234", "title": "1984" }, "rating": 5, "review": "It was a great book", "reviewer_name": "Alice" } ] ``` Written for this site from Chromia’s public course. Code samples are the course’s own. [← Previous**Verify inputs**](https://chromia.com/learn/book-review/input-verification/input-verification/)[Next →**Part 4: Signing transactions and filtering queries**](https://chromia.com/learn/book-review/sign-transaction/)