diff --git a/src/app/dao/BaseDAO.ts b/src/app/dao/BaseDAO.ts
new file mode 100644
index 0000000..20dffe2
--- /dev/null
+++ b/src/app/dao/BaseDAO.ts
@@ -0,0 +1,87 @@
+import { inject } from '@angular/core';
+import { Sqlite } from '../services/sqlite';
+import { QueryResult } from '../types/sqlite.type';
+
+export abstract class BaseDAO<T extends Object, K extends Object, U> {
+  protected readonly sqlite = inject(Sqlite);
+  protected readonly tableName: string;
+
+  constructor(tableName: string) {
+    this.tableName = tableName.toLowerCase();
+  }
+
+  async insert(entity: T) {
+    const params = [];
+    let sql = `INSERT INTO ${this.tableName} ( `;
+    let values = `VALUES ( `;
+    let dbModel = this.toDB(entity);
+    for (let key in dbModel) {
+      if (dbModel[key] !== undefined) {
+        sql += `${key}, `;
+        params.push(dbModel[key]);
+        values += '?, ';
+      }
+    }
+    sql = sql.slice(0, -2);
+    sql += ' ) ';
+    values = values.slice(0, -2);
+    values += ' );';
+    sql = sql + values;
+    const result: { rows: never[] } = await this.sqlite.executeQuery(sql, params);
+    return result;
+  }
+
+  async findBy(values: Partial<K>) {
+    let sql = `SELECT * FROM ${this.tableName} `;
+    const params: any[] = [];
+    const whereSql = this.whereClauseGenerator(values, params);
+    sql += whereSql;
+    sql += ';';
+    const queryResults: QueryResult<U> = await this.sqlite.executeQuery(sql, params);
+    return queryResults.rows.map(this.fromDB);
+  }
+
+  async findAll() {
+    const queryResults: QueryResult<U> = await this.sqlite.executeQuery(
+      `SELECT * FROM ${this.tableName.toLowerCase()}`
+    );
+    return queryResults.rows.map(this.fromDB);
+  }
+
+  async update(values: T, where: Partial<K>) {
+    const params: any[] = [];
+    let sql = `UPDATE ${this.tableName} SET `;
+    let updates = '';
+    let dbModel = this.toDB(values);
+    for (let key in dbModel) {
+      if (dbModel[key] !== undefined) {
+        updates += `${key} = ?, `;
+        params.push(dbModel[key]);
+      }
+    }
+    updates = updates.slice(0, -2);
+    updates += ' ';
+    sql += updates;
+    const whereSql = this.whereClauseGenerator(where, params);
+    sql += whereSql + ';';
+    console.log(sql);
+    const result: { rows: never[] } = await this.sqlite.executeQuery(sql, params);
+    return result;
+  }
+
+  protected whereClauseGenerator(values: Partial<K>, params: any[], alias?: string) {
+    let sql = `WHERE `;
+    const objLength = Object.keys(values).length;
+    let i = 0;
+    for (let key in values) {
+      i += 1;
+      sql += `${alias ? alias + '.' : ''}${key} = ? `;
+      params.push(values[key]);
+      if (i < objLength) sql += `AND `;
+    }
+    return sql;
+  }
+
+  protected abstract toDB(model: T): K;
+  protected abstract fromDB(queryResult: U): T;
+}
diff --git a/src/app/dao/ChainDAO.ts b/src/app/dao/ChainDAO.ts
new file mode 100644
index 0000000..2cf0406
--- /dev/null
+++ b/src/app/dao/ChainDAO.ts
@@ -0,0 +1,21 @@
+import { Injectable } from '@angular/core';
+import { Chain } from '../models/Chain';
+import { BaseDAO } from './BaseDAO';
+import { DBChain } from '../models/db/DBChain';
+
+@Injectable({
+  providedIn: 'root',
+})
+export class ChainDAO extends BaseDAO<Chain, DBChain, DBChain> {
+  constructor() {
+    super(Chain.name);
+  }
+
+  override toDB(model: Chain): DBChain {
+    return new DBChain(model.name, model.image, model.id);
+  }
+
+  override fromDB(qResult: DBChain): Chain {
+    return new Chain(qResult.name, qResult.image, qResult.id);
+  }
+}
diff --git a/src/app/dao/ComposedDAO.ts b/src/app/dao/ComposedDAO.ts
new file mode 100644
index 0000000..9531ed0
--- /dev/null
+++ b/src/app/dao/ComposedDAO.ts
@@ -0,0 +1,28 @@
+import { QueryResult } from '../types/sqlite.type';
+import { BaseDAO } from './BaseDAO';
+
+export abstract class ComposedDAO<T extends Object, K extends Object, U> extends BaseDAO<T, K, U> {
+  protected readonly JOIN_SQL: string;
+  protected readonly tableAlias: string;
+
+  constructor(tableName: string, joinSql: string, tableAlias: string) {
+    super(tableName);
+    this.JOIN_SQL = joinSql;
+    this.tableAlias = tableAlias;
+  }
+
+  override async findAll() {
+    const result: QueryResult<U> = await this.sqlite.executeQuery(this.JOIN_SQL);
+    return result.rows.map(this.fromDB);
+  }
+
+  override async findBy(values: Partial<K>): Promise<T[]> {
+    let sql = this.JOIN_SQL.slice(0, -1) + ' ';
+    const params: any[] = [];
+    const whereSql = this.whereClauseGenerator(values, params, this.tableAlias);
+    sql += whereSql + ';';
+    console.log(sql);
+    const result: QueryResult<U> = await this.sqlite.executeQuery(sql, params);
+    return result.rows.map(this.fromDB);
+  }
+}
diff --git a/src/app/dao/EstablishmentDAO.ts b/src/app/dao/EstablishmentDAO.ts
new file mode 100644
index 0000000..2ccbd10
--- /dev/null
+++ b/src/app/dao/EstablishmentDAO.ts
@@ -0,0 +1,35 @@
+import { Injectable } from '@angular/core';
+import { Establishment } from '../models/Establishment';
+import { Chain } from '../models/Chain';
+import { DBEstablishment } from '../models/db/DBEstablishment';
+import { ComposedDAO } from './ComposedDAO';
+
+@Injectable({
+  providedIn: 'root',
+})
+export class EstablishmentDAO extends ComposedDAO<
+  Establishment,
+  DBEstablishment,
+  EstablishmentQueryResult
+> {
+  constructor() {
+    super(
+      Establishment.name,
+      `SELECT e.id, e.address, chain_id, c.name, c.image FROM establishment e JOIN chain c ON c.id = chain_id;`,
+      'e'
+    );
+  }
+
+  protected override toDB(model: Establishment): DBEstablishment {
+    if (!model.chain.id) throw new Error('Chain id is required');
+    return new DBEstablishment(model.address, model.chain.id, model.id);
+  }
+
+  protected override fromDB(qR: EstablishmentQueryResult): Establishment {
+    const chain = new Chain(qR.name, qR.image, qR.chain_id);
+    return new Establishment(chain, qR.address, qR.id);
+  }
+}
+
+type EstablishmentQueryResult = Omit<Establishment, 'chain'> &
+  Omit<Chain, 'id'> & { id: number; chain_id: number };
diff --git a/src/app/dao/ProductDAO.ts b/src/app/dao/ProductDAO.ts
new file mode 100644
index 0000000..e82ef44
--- /dev/null
+++ b/src/app/dao/ProductDAO.ts
@@ -0,0 +1,21 @@
+import { Injectable } from '@angular/core';
+import { Product } from '../models/Product';
+import { BaseDAO } from './BaseDAO';
+import { DBProduct } from '../models/db/DBProduct';
+
+@Injectable({
+  providedIn: 'root',
+})
+export class ProductDAO extends BaseDAO<Product, DBProduct, DBProduct> {
+  constructor() {
+    super(Product.name);
+  }
+
+  protected override toDB(model: Product): DBProduct {
+    return new Product(model.barcode, model.name, model.image, model.id);
+  }
+
+  protected override fromDB(qR: DBProduct): Product {
+    return new DBProduct(qR.barcode, qR.name, qR.image, qR.id);
+  }
+}
diff --git a/src/app/dao/ProductEstablishmentDAO.ts b/src/app/dao/ProductEstablishmentDAO.ts
new file mode 100644
index 0000000..93a7e33
--- /dev/null
+++ b/src/app/dao/ProductEstablishmentDAO.ts
@@ -0,0 +1,55 @@
+import { Injectable } from '@angular/core';
+import { Establishment } from '../models/Establishment';
+import { Product } from '../models/Product';
+import { ProductEstablishment } from '../models/ProductEstablisment';
+import { Chain } from '../models/Chain';
+import { DBProductEstablishment } from '../models/db/DBProductEstablishment';
+import { ComposedDAO } from './ComposedDAO';
+
+@Injectable({
+  providedIn: 'root',
+})
+export class ProductEstablishmentDAO extends ComposedDAO<
+  ProductEstablishment,
+  DBProductEstablishment,
+  ProductEstablishmentQueryResult
+> {
+  constructor() {
+    super(
+      'product_establishment',
+      `
+    SELECT pe.id, pe.product_id, pe.establishment_id, p.barcode, p.image as product_image, p.name as product_name,
+    e.address, e.chain_id, c.image as chain_image, c.name as chain_name FROM product_establishment pe 
+    JOIN product p ON p.id = pe.product_id 
+    JOIN establishment e ON e.id = pe.establishment_id 
+    JOIN chain c ON c.id = e.chain_id;`,
+      'pe'
+    );
+  }
+
+  protected override toDB(model: ProductEstablishment): DBProductEstablishment {
+    if (!model.product.id) throw new Error('Product id is required');
+    if (!model.establishment.id) throw new Error('Establishment id is required');
+    return new DBProductEstablishment(model.product.id, model.establishment.id, model.id);
+  }
+
+  protected override fromDB(qR: ProductEstablishmentQueryResult): ProductEstablishment {
+    const chain = new Chain(qR.chain_name, qR.chain_image, qR.chain_id);
+    const establishment = new Establishment(chain, qR.address, qR.establishment_id);
+    const product = new Product(qR.barcode, qR.product_name, qR.product_image, qR.product_id);
+    return new ProductEstablishment(product, establishment, qR.id);
+  }
+}
+
+type ProductEstablishmentQueryResult = {
+  address: string;
+  barcode: string;
+  chain_id: number;
+  chain_image: string | null;
+  chain_name: string;
+  establishment_id: number;
+  id: number;
+  product_id: number;
+  product_image: string | null;
+  product_name: string;
+};
diff --git a/src/app/dao/PurchaseDAO.ts b/src/app/dao/PurchaseDAO.ts
new file mode 100644
index 0000000..c342d9e
--- /dev/null
+++ b/src/app/dao/PurchaseDAO.ts
@@ -0,0 +1,63 @@
+import { Injectable } from '@angular/core';
+import { Purchase } from '../models/Purchase';
+import { DBPurchase } from '../models/db/DBPurchase';
+import { Establishment } from '../models/Establishment';
+import { Chain } from '../models/Chain';
+import { Product } from '../models/Product';
+import { ComposedDAO } from './ComposedDAO';
+
+@Injectable({
+  providedIn: 'root',
+})
+export class PurchaseDAO extends ComposedDAO<Purchase, DBPurchase, PurchaseQueryResult> {
+  constructor() {
+    super(
+      Purchase.name,
+      `SELECT p.id, p.price, p.quantity, p.date, p.establishment_id, p.product_id, 
+  pr.barcode, pr.image as product_image, pr.name as product_name, 
+  e.address, e.chain_id, 
+  c.image as chain_image, c.name as chain_name 
+  FROM purchase p 
+  JOIN product pr ON pr.id = p.product_id
+  JOIN establishment e ON e.id = p.establishment_id
+  JOIN chain c ON c.id = e.chain_id;`,
+      'e'
+    );
+  }
+
+  protected override toDB(model: Purchase): DBPurchase {
+    if (!model.establishment.id) throw new Error('Esablishment id is required');
+    if (!model.product.id) throw new Error('Product id is required');
+    return new DBPurchase(
+      model.establishment.id,
+      model.product.id,
+      model.date,
+      model.price * 100,
+      model.quantity,
+      model.id
+    );
+  }
+
+  protected override fromDB(qR: PurchaseQueryResult): Purchase {
+    const chain = new Chain(qR.chain_name, qR.chain_image, qR.chain_id);
+    const establishment = new Establishment(chain, qR.address, qR.establishment_id);
+    const product = new Product(qR.barcode, qR.product_name, qR.product_image, qR.product_id);
+    return new Purchase(establishment, product, qR.price / 100, qR.quantity, qR.date, qR.id);
+  }
+}
+
+type PurchaseQueryResult = {
+  id: number;
+  price: number;
+  quantity: number;
+  date: number;
+  establishment_id: number;
+  product_id: number;
+  barcode: string;
+  product_image: string;
+  product_name: string;
+  address: string;
+  chain_id: number;
+  chain_image: string;
+  chain_name: string;
+};