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Database and CRUD Operations

Quick Summary: Build a complete database with CRUD operations (Create, Read, Update, Delete) to manage a book list using Luna Park.

1. Project Architecture

1. Create two separate folders:
   • Backend: for database and routes
   • Frontend: for user interface

In this tutorial, we start with the backend.

2. Creating the Database

Initialize the database

1. Create a new database named db-books
2. The database contains by default:
   • ID: unique identifier
   • created_at: automatic creation date

Add custom columns

1. Add a title column (type: string)
2. Add an author column (type: string)
3. Add a few rows with test data

In 15 seconds, your database is ready to use!

3. API Routes - General Concept

Routes are URLs that allow you to:

• Retrieve data (GET)
• Send new data (POST)
• Modify existing data (PUT)
• Delete data (DELETE)

We'll create 4 routes corresponding to CRUD operations.

4. GET Route - Retrieve All Books

Create the get-books route

1. Create a new route named get-books
2. Set the method: GET

Simple method: dbfind

1. Create a dbfind node
2. Select the db-books table
3. The result returns an array of rows
4. Connect the result to the response
5. Connect the execution thread between dbfind and the route
6. Test with Execute and Ctrl+Space to visualize

Advanced method: dbfrom with query

1. Create a dbfrom node
2. Select the db-books table
3. Add a select to choose fields:
   • id
   • title
   • author
4. Add a dbexecute
5. Test with Ctrl+Space
6. Connect the result to the response

Type the response (best practice)

1. Define the expected response type:
   • Array of objects
   • Each object contains: id, title, author
2. Advantage: automatic type checking
3. If a field is missing or extra → missingProperty error

5. POST Route - Create a New Book

Create the create-books route

1. Create a new route named create-books
2. Verify the method is POST

Define the body (incoming data)

In Route Input, add a body containing:

• title (string): book title
• author (string): book author

This data will come from frontend inputs

Insert into database

1. Pull a wire from the body
2. Create a dbinsert node
3. Select the db-books table
4. Connect the body to the data field

Return updated state (optional but recommended)

1. Add a dbfind after insertion
2. Select the db-books table
3. Connect the result to the response
4. Copy the response type from get-books (right-click → copy)
5. Paste into create-books response

6. DELETE Route - Delete a Book

Create the delete-books route

1. Create a new route named delete-books
2. Change the method to DELETE
3. Paste the response type (same as get-books)

Define the ID to delete

In Route Input, add a body containing:

• id (string): identifier of the book to delete

Delete by ID

1. Pull a wire from delete-books
2. Create a delete by ID node
3. Select the db-books table
4. Connect the ID:
   • Pull a wire from the body
   • Create a get property
   • Select the id property
   • Connect to the ID field of delete by ID

Return updated state

1. Add a dbfind after deletion
2. Select the db-books table
3. Connect the result to the response

7. PUT Route - Update an Existing Book

Create the update-books route

1. Create a new route named update-books
2. Change the method to PUT
3. Paste the response type

Define the body

In Route Input, add a body containing:

• id (string): book to modify
• title (string): new title
• author (string): new author

Update by ID

1. Pull a wire from update-books
2. Create a DBUpdateByID node
3. Select the db-books table

Handle update data

1. For the ID:

   • Create a spread from the body
   • Select id
   • Connect to the ID field

2. For the data to modify:

   • Create a create object
   • Add title and author properties
   • Create a spread from the body
   • Connect title and author to the object
   • Connect the object to the update field

Return updated state

1. Add a dbfind after the update
2. Select the db-books table
3. Connect the result to the response

Summary of Nodes Used

HTTP Methods

• GET: retrieve data
• POST: create new data
• PUT: modify existing data
• DELETE: delete data

Practical Tips

• Always type responses to avoid structure errors
• Return the current state of the database after each modification
• Use Ctrl+Space to visualize results during development
• The ID is the key to precisely identify each element
• The body transmits data from frontend to backend
• Always verify the HTTP method is correct for each route