Entities

src/products/entities/product.entity.ts

import { Column, CreateDateColumn, Entity, Index, ManyToOne, PrimaryGeneratedColumn, UpdateDateColumn } from 'typeorm';
import { Category } from '../../categories/entities/category.entity';

const decimal = { to: (v: number) => v, from: (v: string | null) => (v === null ? null : Number(v)) };

@Entity('products')
export class Product {
  @PrimaryGeneratedColumn()
  id: number;

  @Index()
  @Column({ length: 120 })
  name: string;

  @Column({ type: 'text', nullable: true })
  description: string | null;

  @Column({ type: 'numeric', precision: 10, scale: 2, transformer: decimal })
  price: number;                         // Postgres returns numeric as string; the transformer fixes that

  @Column({ type: 'int', default: 0 })
  stock: number;

  @ManyToOne(() => Category, (category) => category.products, { nullable: false, onDelete: 'RESTRICT' })
  category: Category;

  @Column()
  categoryId: number;                    // the foreign key as a plain column too

  @CreateDateColumn({ type: 'timestamptz' })
  createdAt: Date;

  @UpdateDateColumn({ type: 'timestamptz' })
  updatedAt: Date;
}

CREATE TABLE "products" (
  "id" SERIAL PRIMARY KEY,
  "name" character varying(120) NOT NULL,
  "description" text,
  "price" numeric(10,2) NOT NULL,
  "stock" integer NOT NULL DEFAULT 0,
  "categoryId" integer NOT NULL REFERENCES "categories"("id") ON DELETE RESTRICT,
  "createdAt" TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT now(),
  "updatedAt" TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT now()
);
CREATE INDEX "IDX_products_name" ON "products" ("name");