diff --git a/README.md b/README.md
index 33db73f..4c8ba4a 100644
--- a/README.md
+++ b/README.md
@@ -5,17 +5,16 @@ CAT – Chorwochenende-Planungs- und Buchungsanwendung.
 ## Inhalt
 
 - PHP-Anwendung aus `/var/www/html/cat`
-- `cat_update_2026-09-19.sql`: idempotentes Datenbank-Update für die Zimmerplanung
-- `cat_update_2026-09-19.zip`: separates Update-Paket der geänderten Webdateien
+- `database/schema.sql`: idempotente, datenfreie Datenbankstruktur mit `CREATE ... IF NOT EXISTS` und kompatiblen `ALTER TABLE ... ADD COLUMN IF NOT EXISTS`-Migrationen
 
 ## Konfiguration
 
 Die produktiven Dateien `inc/db.inc.php` und `inc/mail.inc.php` sind aus Sicherheitsgründen nicht versioniert. Sie müssen auf dem Zielsystem separat konfiguriert werden.
 
-## Datenbank-Update
+## Datenbankstruktur
 
 ```text
-mariadb cat < cat_update_2026-09-19.sql
+mariadb < database/schema.sql
 ```
 
-Das Update legt die drei Zimmeranzahl-Einstellungen an, ohne vorhandene Daten zu überschreiben.
+Die Datei legt Datenbank und Tabellen nur an, wenn sie noch nicht existieren. Für bereits vorhandene Tabellen werden fehlende Spalten mit `ALTER TABLE ... ADD COLUMN IF NOT EXISTS` ergänzt. Es werden keine Datensätze, Administratoren oder Preise angelegt.
diff --git a/database/schema.sql b/database/schema.sql
new file mode 100644
index 0000000..e55f787
--- /dev/null
+++ b/database/schema.sql
@@ -0,0 +1,86 @@
+-- CAT database schema
+-- Schema only: this file creates and evolves structure, but inserts no data.
+-- Safe to run repeatedly on MariaDB.
+
+CREATE DATABASE IF NOT EXISTS cat
+    CHARACTER SET utf8mb4
+    COLLATE utf8mb4_unicode_ci;
+
+USE cat;
+
+CREATE TABLE IF NOT EXISTS participants (
+    id VARCHAR(36) PRIMARY KEY,
+    name VARCHAR(255) NOT NULL,
+    email VARCHAR(255) NOT NULL UNIQUE,
+    allergies TEXT NULL,
+    role VARCHAR(50) NULL CHECK (role IN ('Tagesgast', 'Dauergast')),
+    under_27 TINYINT(1) NOT NULL DEFAULT 0,
+    password_hash VARCHAR(255) NOT NULL
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
+CREATE TABLE IF NOT EXISTS bookings (
+    id INT PRIMARY KEY AUTO_INCREMENT,
+    participant_id VARCHAR(36) NOT NULL,
+    type ENUM('Stay', 'Day') NOT NULL,
+    accommodation_type VARCHAR(50) NULL,
+    meal_preferences TEXT NULL,
+    roommate_requests TEXT NULL,
+    other_notes TEXT NULL,
+    is_paid TINYINT(1) NOT NULL DEFAULT 0,
+    total_price DECIMAL(10,2) NOT NULL DEFAULT 0.00,
+    CONSTRAINT fk_bookings_participant
+        FOREIGN KEY (participant_id) REFERENCES participants(id)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
+CREATE TABLE IF NOT EXISTS admin_users (
+    id INT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
+    username VARCHAR(80) NOT NULL UNIQUE,
+    email VARCHAR(255) NOT NULL,
+    password_hash VARCHAR(255) NOT NULL,
+    is_active TINYINT(1) NOT NULL DEFAULT 1,
+    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
+CREATE TABLE IF NOT EXISTS pricing_settings (
+    id INT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
+    setting_key VARCHAR(80) NOT NULL UNIQUE,
+    price DECIMAL(10,2) NOT NULL DEFAULT 0.00,
+    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
+-- Compatibility migrations for installations whose tables already exist.
+-- ADD COLUMN IF NOT EXISTS leaves existing columns and values untouched.
+ALTER TABLE participants
+    ADD COLUMN IF NOT EXISTS name VARCHAR(255) NOT NULL,
+    ADD COLUMN IF NOT EXISTS email VARCHAR(255) NULL,
+    ADD COLUMN IF NOT EXISTS allergies TEXT NULL,
+    ADD COLUMN IF NOT EXISTS role VARCHAR(50) NULL,
+    ADD COLUMN IF NOT EXISTS under_27 TINYINT(1) NOT NULL DEFAULT 0,
+    ADD COLUMN IF NOT EXISTS password_hash VARCHAR(255) NULL;
+
+ALTER TABLE bookings
+    ADD COLUMN IF NOT EXISTS participant_id VARCHAR(36) NULL,
+    ADD COLUMN IF NOT EXISTS type ENUM('Stay', 'Day') NULL,
+    ADD COLUMN IF NOT EXISTS accommodation_type VARCHAR(50) NULL,
+    ADD COLUMN IF NOT EXISTS meal_preferences TEXT NULL,
+    ADD COLUMN IF NOT EXISTS roommate_requests TEXT NULL,
+    ADD COLUMN IF NOT EXISTS other_notes TEXT NULL,
+    ADD COLUMN IF NOT EXISTS is_paid TINYINT(1) NOT NULL DEFAULT 0,
+    ADD COLUMN IF NOT EXISTS total_price DECIMAL(10,2) NOT NULL DEFAULT 0.00;
+
+ALTER TABLE admin_users
+    ADD COLUMN IF NOT EXISTS username VARCHAR(80) NULL,
+    ADD COLUMN IF NOT EXISTS email VARCHAR(255) NULL,
+    ADD COLUMN IF NOT EXISTS password_hash VARCHAR(255) NULL,
+    ADD COLUMN IF NOT EXISTS is_active TINYINT(1) NOT NULL DEFAULT 1,
+    ADD COLUMN IF NOT EXISTS created_at TIMESTAMP NULL DEFAULT CURRENT_TIMESTAMP,
+    ADD COLUMN IF NOT EXISTS updated_at TIMESTAMP NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;
+
+ALTER TABLE pricing_settings
+    ADD COLUMN IF NOT EXISTS setting_key VARCHAR(80) NULL,
+    ADD COLUMN IF NOT EXISTS price DECIMAL(10,2) NOT NULL DEFAULT 0.00,
+    ADD COLUMN IF NOT EXISTS updated_at TIMESTAMP NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;
+
+-- No participants, bookings, administrators, or pricing rows are inserted here.
+-- Create the first administrator and configure prices through the application.