diff --git a/backend/scheme.sql b/backend/scheme.sql
index e69de29..65b6e12 100644
--- a/backend/scheme.sql
+++ b/backend/scheme.sql
@@ -0,0 +1,54 @@
+CREATE TABLE users (
+    id INT AUTO_INCREMENT PRIMARY KEY,
+    username VARCHAR(100) NOT NULL UNIQUE,
+    password VARCHAR(255) NOT NULL
+);
+
+CREATE TABLE items (
+    id INT AUTO_INCREMENT PRIMARY KEY,
+    item_name VARCHAR(255) NOT NULL UNIQUE,
+    can_borrow_role VARCHAR(255) NOT NULL
+);
+
+CREATE TABLE loans (
+    id INT AUTO_INCREMENT PRIMARY KEY,
+    username VARCHAR(100) NOT NULL,
+    loan_code INT(6) NOT NULL UNIQUE,
+    start_date TIMESTAMP NOT NULL,
+    end_date TIMESTAMP NOT NULL,
+    returned_date TIMESTAMP,
+    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+);
+
+CREATE TABLE lockers (
+    id INT AUTO_INCREMENT PRIMARY KEY,
+    item VARCHAR(255) NOT NULL UNIQUE,
+    locker_number INT NOT NULL UNIQUE
+);
+
+
+-- Mock data
+
+-- Users
+INSERT INTO users (username, password) VALUES
+('alice', 'password123'),
+('bob', 'securepass'),
+('charlie', 'charliepwd');
+
+-- Items
+INSERT INTO items (item_name, can_borrow_role) VALUES
+('Laptop', 'student'),
+('Projector', 'teacher'),
+('Tablet', 'student,teacher');
+
+-- Loans
+INSERT INTO loans (username, loan_code, start_date, end_date, returned_date) VALUES
+('alice', 100001, '2025-08-01 09:00:00', '2025-08-10 17:00:00', NULL),
+('bob', 100002, '2025-08-05 10:00:00', '2025-08-12 15:00:00', '2025-08-12 14:30:00'),
+('charlie', 100003, '2025-08-07 11:00:00', '2025-08-15 16:00:00', NULL);
+
+-- Lockers
+INSERT INTO lockers (item, locker_number) VALUES
+('Laptop', 101),
+('Projector', 102),
+('Tablet', 103);
\ No newline at end of file
diff --git a/docker-compose.yml b/docker-compose.yml
index 3c0748c..808f3ec 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -19,7 +19,7 @@ services:
     environment:
       DB_HOST: mysql
       DB_USER: root
-      DB_PASSWORD: ${MYSQL_ROOT_PASSWORD}
+      DB_PASSWORD: ${DB_PASSWORD}
       DB_NAME: borrow_system
     depends_on:
       - mysql
@@ -32,7 +32,7 @@ services:
     image: mysql:8.0
     restart: unless-stopped
     environment:
-      MYSQL_ROOT_PASSWORD: ${MYSQL_ROOT_PASSWORD}
+      MYSQL_ROOT_PASSWORD: ${DB_PASSWORD}
       MYSQL_DATABASE: borrow_system
     volumes:
       - mysql-data:/var/lib/mysql
diff --git a/other/data_structure.xlsx b/other/data_structure.xlsx
index ccffbad..624b034 100644
Binary files a/other/data_structure.xlsx and b/other/data_structure.xlsx differ