# Part 2: Add a related entity · Your first Rell app on Chromia · Learn Chromia > This lesson starts with the book_review entity. It stores book reviews and ties each one to the book entity. Source: https://chromia.com/learn/book-review/book-review-entity/ Your first Rell app on ChromiaLesson 8 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/) 08 / 26Part 2: Add a related entityBeginner # Part 2: Add a related entity This lesson starts with the `book_review` entity. It stores book reviews and ties each one to the book entity. After that, you add an operation that creates a new book review. The operation takes an ISBN and uses it to attach the review to the matching book. Last, you write a query that returns every review for a given book, looked up by its ISBN. ## In this lesson 1. [Define the book review entity](https://chromia.com/learn/book-review/book-review-entity/tables/) 2. [Add an operation for creating book reviews](https://chromia.com/learn/book-review/book-review-entity/basic-operations/) 3. [Query all reviews for a book](https://chromia.com/learn/book-review/book-review-entity/write-queries/) [Begin lesson →](https://chromia.com/learn/book-review/book-review-entity/tables/) Written for this site from Chromia’s public course. Code samples are the course’s own. [← Previous**Query every book**](https://chromia.com/learn/book-review/book-entity/write-queries/)[Next →**Define the book review entity**](https://chromia.com/learn/book-review/book-review-entity/tables/)