add unique_strings table and trigger for generating unique user codes

database.sql

@@ -30,6 +30,27 @@ CREATE TABLE scanned_tickets (
     UNIQUE (ticket_id)
 );
 
+-- Table for storing unique strings for users
+CREATE TABLE unique_strings (
+    id INT AUTO_INCREMENT PRIMARY KEY,
+    user_id INT NOT NULL,
+    unique_code CHAR(6) NOT NULL UNIQUE,
+    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    FOREIGN KEY (user_id) REFERENCES employees(id) ON DELETE CASCADE
+);
+
+-- Trigger to automatically generate a unique 6-character alphanumeric string for each user
+DELIMITER $$
+CREATE TRIGGER generate_unique_code
+AFTER INSERT ON employees
+FOR EACH ROW
+BEGIN
+    DECLARE unique_code CHAR(6);
+    SET unique_code = (SELECT SUBSTRING(CONCAT(MD5(RAND()), MD5(RAND())), 1, 6));
+    INSERT INTO unique_strings (user_id, unique_code) VALUES (NEW.id, unique_code);
+END$$
+DELIMITER ;
+
 -- Insert a default employee account (username: admin, password: password)
 INSERT INTO employees (username, password_hash)
 VALUES ('admin', SHA2('password', 256)); -- Replace with a secure password hashing method