diff --git a/ajax_handler.php b/ajax_handler.php
index 2f7ff21..85d86a3 100644
--- a/ajax_handler.php
+++ b/ajax_handler.php
@@ -143,7 +143,7 @@ try {
             $role = $stmt->fetchColumn();
             $sender = ($role === 'admin') ? 'admin' : 'user';
 
-            $stmt = $pdo->prepare("INSERT INTO support_messages (user_id, sender, message, is_read) VALUES (?, ?, ?, 0)");
+            $stmt = $pdo->prepare("INSERT INTO support_messages (user_id, sender, message, `is_read`) VALUES (?, ?, ?, 0)");
             $stmt->execute([$target_user_id, $sender, $message]);
             echo json_encode(['code' => 0, 'msg' => '已发送']);
             break;
@@ -159,9 +159,9 @@ try {
             }
 
             if ($isAdmin && (int)$target_user_id !== (int)$_SESSION['user_id']) {
-                $pdo->prepare("UPDATE support_messages SET is_read = 1 WHERE user_id = ? AND sender = 'user'")->execute([$target_user_id]);
+                $pdo->prepare("UPDATE support_messages SET `is_read` = 1 WHERE user_id = ? AND sender = 'user'")->execute([$target_user_id]);
             } else if (!$isAdmin) {
-                $pdo->prepare("UPDATE support_messages SET is_read = 1 WHERE user_id = ? AND sender = 'admin'")->execute([$_SESSION['user_id']]);
+                $pdo->prepare("UPDATE support_messages SET `is_read` = 1 WHERE user_id = ? AND sender = 'admin'")->execute([$_SESSION['user_id']]);
             }
 
             $stmt = $pdo->prepare("SELECT * FROM support_messages WHERE user_id = ? ORDER BY id ASC");
@@ -177,7 +177,7 @@ try {
             // Optimized query to get last message reliably
             $stmt = $pdo->query("
                 SELECT u.id, u.username, m.message as last_message, m.created_at as last_time,
-                (SELECT COUNT(*) FROM support_messages WHERE user_id = u.id AND sender = 'user' AND is_read = 0) as unread_count
+                (SELECT COUNT(*) FROM support_messages WHERE user_id = u.id AND sender = 'user' AND `is_read` = 0) as unread_count
                 FROM users u
                 JOIN (SELECT user_id, MAX(id) as max_id FROM support_messages GROUP BY user_id) last_msg_idx ON u.id = last_msg_idx.user_id
                 JOIN support_messages m ON m.id = last_msg_idx.max_id
@@ -195,14 +195,14 @@ try {
                     SELECT m.*, u.username 
                     FROM support_messages m 
                     JOIN users u ON m.user_id = u.id 
-                    WHERE m.sender = 'user' AND m.is_read = 0 
+                    WHERE m.sender = 'user' AND m.`is_read` = 0 
                     ORDER BY m.id DESC LIMIT 1
                 ");
                 $last_unread = $stmt->fetch(PDO::FETCH_ASSOC);
-                $total_unread = $pdo->query("SELECT COUNT(*) FROM support_messages WHERE sender = 'user' AND is_read = 0")->fetchColumn();
+                $total_unread = $pdo->query("SELECT COUNT(*) FROM support_messages WHERE sender = 'user' AND `is_read` = 0")->fetchColumn();
                 echo json_encode(['code' => 0, 'unread_total' => $total_unread, 'last_user' => $last_unread['username'] ?? '']);
             } else {
-                $stmt = $pdo->prepare("SELECT COUNT(*) FROM support_messages WHERE user_id = ? AND sender = 'admin' AND is_read = 0");
+                $stmt = $pdo->prepare("SELECT COUNT(*) FROM support_messages WHERE user_id = ? AND sender = 'admin' AND `is_read` = 0");
                 $stmt->execute([$_SESSION['user_id']]);
                 echo json_encode(['code' => 0, 'unread_total' => $stmt->fetchColumn()]);
             }
diff --git a/db/schema.sql b/db/schema.sql
index d01b773..1f4cefe 100644
--- a/db/schema.sql
+++ b/db/schema.sql
@@ -14,7 +14,7 @@ CREATE TABLE IF NOT EXISTS recharges (
     txid VARCHAR(255),
     status ENUM('pending', 'completed', 'rejected') DEFAULT 'pending',
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-    FOREIGN KEY (user_id) REFERENCES users(id)
+    FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
 );
 
 CREATE TABLE IF NOT EXISTS sms_orders (
@@ -29,7 +29,7 @@ CREATE TABLE IF NOT EXISTS sms_orders (
     status ENUM('pending', 'received', 'canceled', 'expired') DEFAULT 'pending',
     expire_at TIMESTAMP NULL,
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-    FOREIGN KEY (user_id) REFERENCES users(id)
+    FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
 );
 
 CREATE TABLE IF NOT EXISTS settings (
@@ -43,8 +43,9 @@ CREATE TABLE IF NOT EXISTS support_messages (
     user_id INT NOT NULL,
     sender ENUM('user', 'admin') NOT NULL,
     message TEXT NOT NULL,
+    is_read TINYINT(1) DEFAULT 0,
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-    FOREIGN KEY (user_id) REFERENCES users(id)
+    FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
 );
 
 -- Default Settings
@@ -60,4 +61,4 @@ ON DUPLICATE KEY UPDATE setting_value = VALUES(setting_value);
 -- Default Admin (admin / admin123)
 INSERT INTO users (username, password_hash, role) VALUES 
 ('admin', '$2y$10$QbKYSCqJI0WQLyf6NNSML.ukYrOZ0MdY61ZpK7Ekn5QQ/A9oDr.hu', 'admin')
-ON DUPLICATE KEY UPDATE role = 'admin';
\ No newline at end of file
+ON DUPLICATE KEY UPDATE role = 'admin';