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using { cuid, managed } from '@sap/cds/common';

namespace my.bookshop;

entity Books : cuid, managed {
  title       : String(111) not null;
  author      : Association to Authors;
  stock       : Integer;
  price       : Decimal(9,2);
}

entity Authors : cuid, managed {
  name        : String(111);
  books       : Association to many Books on books.author = $self;
}

using { my.bookshop as my } from '../db/schema';

service CatalogService @(path: '/browse') {
  @readonly entity Books as projection on my.Books;
  @readonly entity Authors as projection on my.Authors;
  
  @requires: 'authenticated-user'
  action submitOrder(book: Books:ID, quantity: Integer) returns String;
}

project/
├── app/              # UI content (Fiori, UI5)
├── srv/              # Service definitions (.cds, .js/.ts)
├── db/               # Data models and schema
│   ├── schema.cds    # Entity definitions
│   └── data/         # CSV seed data
├── package.json      # Dependencies and CDS config
└── .cdsrc.json       # CDS configuration (optional)

using { cuid, managed, temporal } from '@sap/cds/common';
// cuid = UUID key
// managed = createdAt, createdBy, modifiedAt, modifiedBy
// temporal = validFrom, validTo

// srv/cat-service.js
module.exports = class CatalogService extends cds.ApplicationService {
  init() {
    const { Books } = this.entities;
    
    // Before handlers - validation
    this.before('CREATE', Books, req => {
      if (!req.data.title) req.error(400, 'Title required');
    });
    
    // On handlers - custom logic
    this.on('submitOrder', async req => {
      const { book, quantity } = req.data;
      // Custom business logic
      return { success: true };
    });
    
    return super.init();
  }
}

const { Books } = cds.entities;

// SELECT with conditions
const books = await SELECT.from(Books)
  .where({ stock: { '>': 0 } })
  .orderBy('title');

// INSERT
await INSERT.into(Books)
  .entries({ title: 'New Book', stock: 10 });

// UPDATE
await UPDATE(Books, bookId)
  .set({ stock: { '-=': 1 } });

// package.json
{
  "cds": {
    "requires": {
      "db": {
        "[development]": { 
          "kind": "sqlite", 
          "credentials": { "url": ":memory:" } 
        },
        "[production]": { "kind": "hana" }
      }
    }
  }
}

cds add hana
cds deploy --to hana

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cds add multitenancy

{
  "cds": {
    "requires": {
      "multitenancy": true
    }
  }
}

// Service-level
@requires: 'authenticated-user'
service CatalogService { ... }

// Entity-level
@restrict: [
  { grant: 'READ' },
  { grant: 'WRITE', to: 'admin' }
]
entity Books { ... }

cds init [name]           # Create project
cds add <feature>         # Add capability
cds watch                 # Dev server with live reload
cds serve                 # Start server
cds compile <model>       # Compile CDS to CSN/SQL/EDMX
cds deploy --to hana      # Deploy to HANA
cds build                 # Build for deployment
cds env                   # Show configuration
cds repl                  # Interactive REPL
cds version               # Show version info