Fix backend user contract and add User-Employee-Customer linkage

- Add active field to User entity and users table
- Add userId linkage to Employee and Customer entities with unique constraints and FKs
- Add repository methods findByUserId and findAllByEmail
- Create UserBusinessLinkageService for shared employee/customer creation logic
- Create AuthenticationHelper utility for resolving authenticated users
- Update UserService to persist all user fields and create linked business entities
- Update AuthController register to set active and create linked customer
- Update DataInitializer to be idempotent and use shared linkage service
- Update Postman collection user endpoints with fullName, email, and active

petshop-api.postman_collection.json

@@ -1435,7 +1435,7 @@
             ],
             "body": {
               "mode": "raw",
-              "raw": "{\n  \"username\": \"newuser\",\n  \"password\": \"password123\",\n  \"role\": \"STAFF\"\n}"
+              "raw": "{\n  \"username\": \"newuser\",\n  \"password\": \"password123\",\n  \"fullName\": \"New User\",\n  \"email\": \"newuser@petshop.com\",\n  \"role\": \"STAFF\",\n  \"active\": true\n}"
             }
           }
         },
@@ -1457,7 +1457,7 @@
             ],
             "body": {
               "mode": "raw",
-              "raw": "{\n  \"username\": \"user1\",\n  \"role\": \"STAFF\"\n}"
+              "raw": "{\n  \"username\": \"user1\",\n  \"password\": \"newpassword123\",\n  \"fullName\": \"Updated User\",\n  \"email\": \"user1@petshop.com\",\n  \"role\": \"STAFF\",\n  \"active\": true\n}"
             }
           }
         },

src/main/java/com/petshop/backend/config/DataInitializer.java

@@ -2,6 +2,7 @@ package com.petshop.backend.config;
 
 import com.petshop.backend.entity.User;
 import com.petshop.backend.repository.UserRepository;
+import com.petshop.backend.service.UserBusinessLinkageService;
 import org.springframework.boot.CommandLineRunner;
 import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.stereotype.Component;
@@ -11,57 +12,137 @@ public class DataInitializer implements CommandLineRunner {
 
     private final UserRepository userRepository;
     private final PasswordEncoder passwordEncoder;
+    private final UserBusinessLinkageService userBusinessLinkageService;
 
-    public DataInitializer(UserRepository userRepository, PasswordEncoder passwordEncoder) {
+    public DataInitializer(UserRepository userRepository, PasswordEncoder passwordEncoder, UserBusinessLinkageService userBusinessLinkageService) {
         this.userRepository = userRepository;
         this.passwordEncoder = passwordEncoder;
+        this.userBusinessLinkageService = userBusinessLinkageService;
     }
 
     @Override
     public void run(String... args) {
         System.out.println("==== DataInitializer: Starting user creation ====");
 
-        if (userRepository.findByUsername("admin").isEmpty()) {
+        User admin = userRepository.findByUsername("admin").orElse(null);
+        if (admin == null) {
             System.out.println("Creating admin user...");
-            User admin = new User();
+            admin = new User();
             admin.setUsername("admin");
             admin.setPassword(passwordEncoder.encode("admin123"));
             admin.setEmail("admin@petshop.com");
             admin.setFullName("Admin User");
             admin.setRole(User.Role.ADMIN);
-            userRepository.save(admin);
+            admin.setActive(true);
+            admin = userRepository.save(admin);
             System.out.println("Admin user created successfully");
         } else {
             System.out.println("Admin user already exists");
+            // Normalize missing fields if needed
+            boolean updated = false;
+            if (admin.getFullName() == null || admin.getFullName().isEmpty()) {
+                admin.setFullName("Admin User");
+                updated = true;
             }
+            if (admin.getEmail() == null || admin.getEmail().isEmpty()) {
+                admin.setEmail("admin@petshop.com");
+                updated = true;
+            }
+            if (admin.getActive() == null) {
+                admin.setActive(true);
+                updated = true;
+            }
+            if (admin.getRole() == null) {
+                admin.setRole(User.Role.ADMIN);
+                updated = true;
+            }
+            if (updated) {
+                admin = userRepository.save(admin);
+                System.out.println("Admin user normalized");
+            }
+        }
+        // Ensure linked employee
+        userBusinessLinkageService.ensureLinkedEmployee(admin);
 
-        if (userRepository.findByUsername("staff").isEmpty()) {
+        User staff = userRepository.findByUsername("staff").orElse(null);
+        if (staff == null) {
             System.out.println("Creating staff user...");
-            User staff = new User();
+            staff = new User();
             staff.setUsername("staff");
             staff.setPassword(passwordEncoder.encode("staff123"));
             staff.setEmail("staff@petshop.com");
             staff.setFullName("Staff User");
             staff.setRole(User.Role.STAFF);
-            userRepository.save(staff);
+            staff.setActive(true);
+            staff = userRepository.save(staff);
             System.out.println("Staff user created successfully");
         } else {
             System.out.println("Staff user already exists");
+            // Normalize missing fields if needed
+            boolean updated = false;
+            if (staff.getFullName() == null || staff.getFullName().isEmpty()) {
+                staff.setFullName("Staff User");
+                updated = true;
             }
+            if (staff.getEmail() == null || staff.getEmail().isEmpty()) {
+                staff.setEmail("staff@petshop.com");
+                updated = true;
+            }
+            if (staff.getActive() == null) {
+                staff.setActive(true);
+                updated = true;
+            }
+            if (staff.getRole() == null) {
+                staff.setRole(User.Role.STAFF);
+                updated = true;
+            }
+            if (updated) {
+                staff = userRepository.save(staff);
+                System.out.println("Staff user normalized");
+            }
+        }
+        // Ensure linked employee
+        userBusinessLinkageService.ensureLinkedEmployee(staff);
 
-        if (userRepository.findByUsername("customer").isEmpty()) {
+        User customer = userRepository.findByUsername("customer").orElse(null);
+        if (customer == null) {
             System.out.println("Creating customer user...");
-            User customer = new User();
+            customer = new User();
             customer.setUsername("customer");
             customer.setPassword(passwordEncoder.encode("customer123"));
             customer.setEmail("customer@petshop.com");
             customer.setFullName("Test Customer");
             customer.setRole(User.Role.CUSTOMER);
-            userRepository.save(customer);
+            customer.setActive(true);
+            customer = userRepository.save(customer);
             System.out.println("Customer user created successfully");
         } else {
             System.out.println("Customer user already exists");
+            // Normalize missing fields if needed
+            boolean updated = false;
+            if (customer.getFullName() == null || customer.getFullName().isEmpty()) {
+                customer.setFullName("Test Customer");
+                updated = true;
             }
+            if (customer.getEmail() == null || customer.getEmail().isEmpty()) {
+                customer.setEmail("customer@petshop.com");
+                updated = true;
+            }
+            if (customer.getActive() == null) {
+                customer.setActive(true);
+                updated = true;
+            }
+            if (customer.getRole() == null) {
+                customer.setRole(User.Role.CUSTOMER);
+                updated = true;
+            }
+            if (updated) {
+                customer = userRepository.save(customer);
+                System.out.println("Customer user normalized");
+            }
+        }
+        // Ensure linked customer
+        userBusinessLinkageService.ensureLinkedCustomer(customer);
 
         System.out.println("==== DataInitializer: Completed ====");
     }

src/main/java/com/petshop/backend/controller/AuthController.java

@@ -10,6 +10,7 @@ import com.petshop.backend.dto.auth.UserInfoResponse;
 import com.petshop.backend.entity.User;
 import com.petshop.backend.repository.UserRepository;
 import com.petshop.backend.security.JwtUtil;
+import com.petshop.backend.service.UserBusinessLinkageService;
 import jakarta.validation.Valid;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
@@ -42,12 +43,14 @@ public class AuthController {
     private final UserRepository userRepository;
     private final JwtUtil jwtUtil;
     private final PasswordEncoder passwordEncoder;
+    private final UserBusinessLinkageService userBusinessLinkageService;
 
-    public AuthController(AuthenticationManager authenticationManager, UserRepository userRepository, JwtUtil jwtUtil, PasswordEncoder passwordEncoder) {
+    public AuthController(AuthenticationManager authenticationManager, UserRepository userRepository, JwtUtil jwtUtil, PasswordEncoder passwordEncoder, UserBusinessLinkageService userBusinessLinkageService) {
         this.authenticationManager = authenticationManager;
         this.userRepository = userRepository;
         this.jwtUtil = jwtUtil;
         this.passwordEncoder = passwordEncoder;
+        this.userBusinessLinkageService = userBusinessLinkageService;
     }
 
     @PostMapping("/register")
@@ -70,9 +73,13 @@ public class AuthController {
         user.setEmail(request.getEmail());
         user.setFullName(request.getFullName());
         user.setRole(User.Role.CUSTOMER);
+        user.setActive(true);
 
         User savedUser = userRepository.save(user);
 
+        // Create or link customer record
+        userBusinessLinkageService.ensureLinkedCustomer(savedUser);
+
         UserDetails userDetails = new org.springframework.security.core.userdetails.User(
                 savedUser.getUsername(),
                 savedUser.getPassword(),

src/main/java/com/petshop/backend/entity/Customer.java

@@ -15,6 +15,9 @@ public class Customer {
     @GeneratedValue(strategy = GenerationType.IDENTITY)
     private Long customerId;
 
+    @Column(name = "user_id")
+    private Long userId;
+
     @Column(nullable = false, length = 50)
     private String firstName;
 
@@ -38,8 +41,9 @@ public class Customer {
     public Customer() {
     }
 
-    public Customer(Long customerId, String firstName, String lastName, String email, String phone, LocalDateTime createdAt, LocalDateTime updatedAt) {
+    public Customer(Long customerId, Long userId, String firstName, String lastName, String email, String phone, LocalDateTime createdAt, LocalDateTime updatedAt) {
         this.customerId = customerId;
+        this.userId = userId;
         this.firstName = firstName;
         this.lastName = lastName;
         this.email = email;
@@ -56,6 +60,14 @@ public class Customer {
         this.customerId = customerId;
     }
 
+    public Long getUserId() {
+        return userId;
+    }
+
+    public void setUserId(Long userId) {
+        this.userId = userId;
+    }
+
     public String getFirstName() {
         return firstName;
     }
@@ -121,6 +133,7 @@ public class Customer {
     public String toString() {
         return "Customer{" +
                 "customerId=" + customerId +
+                ", userId=" + userId +
                 ", firstName='" + firstName + '\'' +
                 ", lastName='" + lastName + '\'' +
                 ", email='" + email + '\'' +

src/main/java/com/petshop/backend/entity/Employee.java

@@ -15,6 +15,9 @@ public class Employee {
     @GeneratedValue(strategy = GenerationType.IDENTITY)
     private Long employeeId;
 
+    @Column(name = "user_id")
+    private Long userId;
+
     @Column(nullable = false, length = 50)
     private String firstName;
 
@@ -44,8 +47,9 @@ public class Employee {
     public Employee() {
     }
 
-    public Employee(Long employeeId, String firstName, String lastName, String email, String phone, String role, Boolean isActive, LocalDateTime createdAt, LocalDateTime updatedAt) {
+    public Employee(Long employeeId, Long userId, String firstName, String lastName, String email, String phone, String role, Boolean isActive, LocalDateTime createdAt, LocalDateTime updatedAt) {
         this.employeeId = employeeId;
+        this.userId = userId;
         this.firstName = firstName;
         this.lastName = lastName;
         this.email = email;
@@ -64,6 +68,14 @@ public class Employee {
         this.employeeId = employeeId;
     }
 
+    public Long getUserId() {
+        return userId;
+    }
+
+    public void setUserId(Long userId) {
+        this.userId = userId;
+    }
+
     public String getFirstName() {
         return firstName;
     }
@@ -145,6 +157,7 @@ public class Employee {
     public String toString() {
         return "Employee{" +
                 "employeeId=" + employeeId +
+                ", userId=" + userId +
                 ", firstName='" + firstName + '\'' +
                 ", lastName='" + lastName + '\'' +
                 ", email='" + email + '\'' +

src/main/java/com/petshop/backend/entity/User.java

@@ -34,6 +34,9 @@ public class User {
     @Column(nullable = false, length = 20, columnDefinition = "VARCHAR(20)")
     private Role role;
 
+    @Column(nullable = false)
+    private Boolean active = true;
+
     @CreationTimestamp
     @Column(name = "created_at", updatable = false)
     private LocalDateTime createdAt;
@@ -49,7 +52,7 @@ public class User {
     public User() {
     }
 
-    public User(Long id, String username, String password, String email, String fullName, String avatarUrl, Role role, LocalDateTime createdAt, LocalDateTime updatedAt) {
+    public User(Long id, String username, String password, String email, String fullName, String avatarUrl, Role role, Boolean active, LocalDateTime createdAt, LocalDateTime updatedAt) {
         this.id = id;
         this.username = username;
         this.password = password;
@@ -57,6 +60,7 @@ public class User {
         this.fullName = fullName;
         this.avatarUrl = avatarUrl;
         this.role = role;
+        this.active = active;
         this.createdAt = createdAt;
         this.updatedAt = updatedAt;
     }
@@ -117,6 +121,14 @@ public class User {
         this.role = role;
     }
 
+    public Boolean getActive() {
+        return active;
+    }
+
+    public void setActive(Boolean active) {
+        this.active = active;
+    }
+
     public LocalDateTime getCreatedAt() {
         return createdAt;
     }
@@ -156,6 +168,7 @@ public class User {
                 ", fullName='" + fullName + '\'' +
                 ", avatarUrl='" + avatarUrl + '\'' +
                 ", role=" + role +
+                ", active=" + active +
                 ", createdAt=" + createdAt +
                 ", updatedAt=" + updatedAt +
                 '}';

src/main/java/com/petshop/backend/repository/CustomerRepository.java

@@ -8,9 +8,15 @@ import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.query.Param;
 import org.springframework.stereotype.Repository;
 
+import java.util.List;
+import java.util.Optional;
+
 @Repository
 public interface CustomerRepository extends JpaRepository<Customer, Long> {
 
+    Optional<Customer> findByUserId(Long userId);
+    List<Customer> findAllByEmail(String email);
+
     @Query("SELECT c FROM Customer c WHERE " +
            "LOWER(c.firstName) LIKE LOWER(CONCAT('%', :q, '%')) OR " +
            "LOWER(c.lastName) LIKE LOWER(CONCAT('%', :q, '%')) OR " +

src/main/java/com/petshop/backend/repository/EmployeeRepository.java

@@ -4,6 +4,11 @@ import com.petshop.backend.entity.Employee;
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.stereotype.Repository;
 
+import java.util.List;
+import java.util.Optional;
+
 @Repository
 public interface EmployeeRepository extends JpaRepository<Employee, Long> {
+    Optional<Employee> findByUserId(Long userId);
+    List<Employee> findAllByEmail(String email);
 }

src/main/java/com/petshop/backend/service/UserBusinessLinkageService.java

@@ -0,0 +1,138 @@
+package com.petshop.backend.service;
+
+import com.petshop.backend.entity.Customer;
+import com.petshop.backend.entity.Employee;
+import com.petshop.backend.entity.User;
+import com.petshop.backend.repository.CustomerRepository;
+import com.petshop.backend.repository.EmployeeRepository;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.util.List;
+
+@Service
+public class UserBusinessLinkageService {
+
+    private final EmployeeRepository employeeRepository;
+    private final CustomerRepository customerRepository;
+
+    @Autowired
+    public UserBusinessLinkageService(EmployeeRepository employeeRepository, CustomerRepository customerRepository) {
+        this.employeeRepository = employeeRepository;
+        this.customerRepository = customerRepository;
+    }
+
+    @Transactional
+    public Employee ensureLinkedEmployee(User user) {
+        // Check if already linked
+        if (user.getId() != null) {
+            var existing = employeeRepository.findByUserId(user.getId());
+            if (existing.isPresent()) {
+                return existing.get();
+            }
+        }
+
+        // Check for email matches
+        List<Employee> emailMatches = employeeRepository.findAllByEmail(user.getEmail());
+
+        // If exactly one match exists and has no userId, link it
+        if (emailMatches.size() == 1) {
+            Employee employee = emailMatches.get(0);
+            if (employee.getUserId() == null) {
+                employee.setUserId(user.getId());
+                return employeeRepository.save(employee);
+            }
+        }
+
+        // Otherwise create a new linked Employee
+        Employee newEmployee = new Employee();
+        newEmployee.setUserId(user.getId());
+        newEmployee.setEmail(user.getEmail());
+
+        // Split fullName into firstName and lastName
+        String[] nameParts = splitFullName(user.getFullName());
+        newEmployee.setFirstName(nameParts[0]);
+        newEmployee.setLastName(nameParts[1]);
+
+        // Set required fields with deterministic values
+        newEmployee.setPhone("000-000-0000");
+        newEmployee.setIsActive(true);
+
+        // Map role based on user role
+        if (user.getRole() == User.Role.ADMIN) {
+            newEmployee.setRole("Manager");
+        } else if (user.getRole() == User.Role.STAFF) {
+            newEmployee.setRole("Staff");
+        } else {
+            newEmployee.setRole("Staff"); // fallback
+        }
+
+        return employeeRepository.save(newEmployee);
+    }
+
+    @Transactional
+    public Customer ensureLinkedCustomer(User user) {
+        // Check if already linked
+        if (user.getId() != null) {
+            var existing = customerRepository.findByUserId(user.getId());
+            if (existing.isPresent()) {
+                return existing.get();
+            }
+        }
+
+        // Check for email matches
+        List<Customer> emailMatches = customerRepository.findAllByEmail(user.getEmail());
+
+        // If exactly one match exists and has no userId, link it
+        if (emailMatches.size() == 1) {
+            Customer customer = emailMatches.get(0);
+            if (customer.getUserId() == null) {
+                customer.setUserId(user.getId());
+                return customerRepository.save(customer);
+            }
+        }
+
+        // Otherwise create a new linked Customer
+        Customer newCustomer = new Customer();
+        newCustomer.setUserId(user.getId());
+        newCustomer.setEmail(user.getEmail());
+
+        // Split fullName into firstName and lastName
+        String[] nameParts = splitFullName(user.getFullName());
+        newCustomer.setFirstName(nameParts[0]);
+        newCustomer.setLastName(nameParts[1]);
+
+        // Set required fields with deterministic values
+        newCustomer.setPhone("000-000-0001");
+
+        return customerRepository.save(newCustomer);
+    }
+
+    private String[] splitFullName(String fullName) {
+        if (fullName == null || fullName.trim().isEmpty()) {
+            return new String[]{"System", "User"};
+        }
+
+        String trimmed = fullName.trim();
+        int spaceIndex = trimmed.indexOf(' ');
+
+        if (spaceIndex == -1) {
+            // Single token
+            return new String[]{trimmed, "User"};
+        }
+
+        // Multiple tokens
+        String firstName = trimmed.substring(0, spaceIndex).trim();
+        String lastName = trimmed.substring(spaceIndex + 1).trim();
+
+        if (firstName.isEmpty()) {
+            firstName = "System";
+        }
+        if (lastName.isEmpty()) {
+            lastName = "User";
+        }
+
+        return new String[]{firstName, lastName};
+    }
+}

src/main/java/com/petshop/backend/service/UserService.java

@@ -17,10 +17,12 @@ public class UserService {
 
     private final UserRepository userRepository;
     private final PasswordEncoder passwordEncoder;
+    private final UserBusinessLinkageService userBusinessLinkageService;
 
-    public UserService(UserRepository userRepository, PasswordEncoder passwordEncoder) {
+    public UserService(UserRepository userRepository, PasswordEncoder passwordEncoder, UserBusinessLinkageService userBusinessLinkageService) {
         this.userRepository = userRepository;
         this.passwordEncoder = passwordEncoder;
+        this.userBusinessLinkageService = userBusinessLinkageService;
     }
 
     public Page<UserResponse> getAllUsers(String query, Pageable pageable) {
@@ -44,9 +46,20 @@ public class UserService {
         User user = new User();
         user.setUsername(request.getUsername());
         user.setPassword(passwordEncoder.encode(request.getPassword()));
+        user.setFullName(request.getFullName());
+        user.setEmail(request.getEmail());
         user.setRole(request.getRole());
+        user.setActive(request.getActive() != null ? request.getActive() : true);
 
         user = userRepository.save(user);
+
+        // Create or link business entity based on role
+        if (user.getRole() == User.Role.STAFF || user.getRole() == User.Role.ADMIN) {
+            userBusinessLinkageService.ensureLinkedEmployee(user);
+        } else if (user.getRole() == User.Role.CUSTOMER) {
+            userBusinessLinkageService.ensureLinkedCustomer(user);
+        }
+
         return mapToResponse(user);
     }
 
@@ -59,7 +72,10 @@ public class UserService {
         if (request.getPassword() != null && !request.getPassword().trim().isEmpty()) {
             user.setPassword(passwordEncoder.encode(request.getPassword()));
         }
+        user.setFullName(request.getFullName());
+        user.setEmail(request.getEmail());
         user.setRole(request.getRole());
+        user.setActive(request.getActive() != null ? request.getActive() : true);
 
         user = userRepository.save(user);
         return mapToResponse(user);
@@ -82,7 +98,12 @@ public class UserService {
         UserResponse response = new UserResponse();
         response.setId(user.getId());
         response.setUsername(user.getUsername());
+        response.setFullName(user.getFullName());
+        response.setEmail(user.getEmail());
         response.setRole(user.getRole().toString());
+        response.setActive(user.getActive());
+        response.setCreatedAt(user.getCreatedAt());
+        response.setUpdatedAt(user.getUpdatedAt());
         return response;
     }
 }

src/main/java/com/petshop/backend/util/AuthenticationHelper.java

@@ -0,0 +1,38 @@
+package com.petshop.backend.util;
+
+import com.petshop.backend.entity.Customer;
+import com.petshop.backend.entity.Employee;
+import com.petshop.backend.entity.User;
+import com.petshop.backend.repository.CustomerRepository;
+import com.petshop.backend.repository.EmployeeRepository;
+import com.petshop.backend.repository.UserRepository;
+import org.springframework.security.core.Authentication;
+import org.springframework.security.core.context.SecurityContextHolder;
+import org.springframework.stereotype.Component;
+
+@Component
+public class AuthenticationHelper {
+
+    public static User getAuthenticatedUser(UserRepository userRepository) {
+        Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
+        if (authentication == null || !authentication.isAuthenticated()) {
+            throw new RuntimeException("No authenticated user found");
+        }
+
+        String username = authentication.getName();
+        return userRepository.findByUsername(username)
+                .orElseThrow(() -> new RuntimeException("User not found: " + username));
+    }
+
+    public static Employee getAuthenticatedEmployee(UserRepository userRepository, EmployeeRepository employeeRepository) {
+        User user = getAuthenticatedUser(userRepository);
+        return employeeRepository.findByUserId(user.getId())
+                .orElseThrow(() -> new RuntimeException("Employee record not found for user: " + user.getUsername()));
+    }
+
+    public static Customer getAuthenticatedCustomer(UserRepository userRepository, CustomerRepository customerRepository) {
+        User user = getAuthenticatedUser(userRepository);
+        return customerRepository.findByUserId(user.getId())
+                .orElseThrow(() -> new RuntimeException("Customer record not found for user: " + user.getUsername()));
+    }
+}

src/main/resources/schema.sql

@@ -12,6 +12,7 @@ CREATE TABLE IF NOT EXISTS storeLocation (
 
 CREATE TABLE IF NOT EXISTS employee (
     employeeId BIGINT AUTO_INCREMENT PRIMARY KEY,
+    user_id BIGINT NULL,
     firstName VARCHAR(50) NOT NULL,
     lastName VARCHAR(50) NOT NULL,
     email VARCHAR(100) NOT NULL,
@@ -19,7 +20,8 @@ CREATE TABLE IF NOT EXISTS employee (
     role VARCHAR(50) NOT NULL,
     isActive BOOLEAN DEFAULT TRUE NOT NULL,
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
+    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+    CONSTRAINT uk_employee_user_id UNIQUE (user_id)
 );
 
 CREATE TABLE IF NOT EXISTS employeeStore (
@@ -32,12 +34,14 @@ CREATE TABLE IF NOT EXISTS employeeStore (
 
 CREATE TABLE IF NOT EXISTS customer (
     customerId BIGINT AUTO_INCREMENT PRIMARY KEY,
+    user_id BIGINT NULL,
     firstName VARCHAR(50) NOT NULL,
     lastName VARCHAR(50) NOT NULL,
     email VARCHAR(100) NOT NULL,
     phone VARCHAR(20) NOT NULL,
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
+    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+    CONSTRAINT uk_customer_user_id UNIQUE (user_id)
 );
 
 CREATE TABLE IF NOT EXISTS pet (
@@ -201,6 +205,7 @@ CREATE TABLE IF NOT EXISTS users (
     fullName VARCHAR(100),
     avatarUrl VARCHAR(255),
     role VARCHAR(20) NOT NULL,
+    active BOOLEAN NOT NULL DEFAULT TRUE,
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
     updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
 );
@@ -239,3 +244,7 @@ CREATE TABLE IF NOT EXISTS message (
     FOREIGN KEY (conversationId) REFERENCES conversation(id),
     FOREIGN KEY (senderId) REFERENCES users(id)
 );
+
+-- Add foreign keys for user_id linkage
+ALTER TABLE employee ADD CONSTRAINT fk_employee_user_id FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE SET NULL;
+ALTER TABLE customer ADD CONSTRAINT fk_customer_user_id FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE SET NULL;