diff --git a/doc b/doc
index 5335524..2ce0e26 160000
--- a/doc
+++ b/doc
@@ -1 +1 @@
-Subproject commit 5335524d3e57c7551f31c7e21fc04c464b23429a
+Subproject commit 2ce0e26b101192b92061c299ffc0e5524104f215
diff --git a/matemat/db/facade.py b/matemat/db/facade.py
index 67f1c5f..64418d9 100644
--- a/matemat/db/facade.py
+++ b/matemat/db/facade.py
@@ -232,7 +232,7 @@ class MatematDatabase(object):
                 'tkhash': tkhash
             })
 
-    def change_user(self, user: User, **kwargs)\
+    def change_user(self, user: User, agent: User, **kwargs)\
             -> None:
         """
         Commit changes to the user in the database.  If writing the requested changes succeeded, the values are updated
@@ -240,6 +240,7 @@ class MatematDatabase(object):
         the ID field in the provided user object.
 
         :param user: The user object to update and to identify the requested user by.
+        :param agent: The user that is performing the change.
         :param kwargs: The properties to change.
         :raises DatabaseConsistencyError: If the user represented by the object does not exist.
         """
@@ -250,6 +251,25 @@ class MatematDatabase(object):
         is_admin: bool = kwargs['is_admin'] if 'is_admin' in kwargs else user.is_admin
         is_member: bool = kwargs['is_member'] if 'is_member' in kwargs else user.is_member
         with self.db.transaction() as c:
+            c.execute('SELECT balance FROM users WHERE user_id = :user_id', {'user_id': user.id})
+            row = c.fetchone()
+            if row is None:
+                raise DatabaseConsistencyError(f'User with ID {user.id} does not exist')
+            oldbalance: int = row[0]
+            if balance != oldbalance:
+                c.execute('''
+                INSERT INTO transactions (user_id, value, old_balance)
+                  VALUES (:user_id, :value, :old_balance)
+                ''', {
+                    'user_id': user.id,
+                    'value': balance - oldbalance,
+                    'old_balance': oldbalance
+                })
+                # TODO: Implement reason field
+                c.execute('''
+                INSERT INTO modifications (ta_id, agent_id, reason)
+                  VALUES (last_insert_rowid(), :agent_id, NULL)
+                ''', {'agent_id': agent.id})
             c.execute('''
             UPDATE users SET
               username = :username,
@@ -411,60 +431,38 @@ class MatematDatabase(object):
                 raise DatabaseConsistencyError(
                     f'delete_product should affect 1 products row, but affected {affected}')
 
-    def increment_consumption(self, user: User, product: Product, count: int = 1) -> None:
+    def increment_consumption(self, user: User, product: Product) -> None:
         """
         Decrement the user's balance by the price of the product, decrement the products stock, and create an entry in
         the statistics table.
+
         :param user: The user buying a product.
         :param product: The product the user is buying.
-        :param count: How many units of the product the user is buying, defaults to 1.
         :raises DatabaseConsistencyError: If the user or the product does not exist in the database.
         """
+        price: int = product.price_member if user.is_member else product.price_non_member
         with self.db.transaction() as c:
-            # Retrieve the consumption entry for the (user, product) pair, if any.
             c.execute('''
-            SELECT count
-            FROM consumption
-            WHERE user_id = :user_id
-              AND product_id = :product_id
+            INSERT INTO transactions (user_id, value, old_balance)
+              VALUES (:user_id, :value, :old_balance)
             ''', {
                 'user_id': user.id,
+                'value': -price,
+                'old_balance': user.balance
+            })
+            c.execute('''
+            INSERT INTO consumptions (ta_id, product_id)
+              VALUES (last_insert_rowid(), :product_id)
+            ''', {
                 'product_id': product.id
             })
-            row = c.fetchone()
-            if row is None:
-                # If the entry does not exist, create a new one.
-                c.execute('''
-                INSERT INTO consumption (user_id, product_id, count)
-                VALUES (:user_id, :product_id, :count)
-                ''', {
-                    'user_id': user.id,
-                    'product_id': product.id,
-                    'count': count
-                })
-            else:
-                # If the entry exists, update the consumption count.
-                c.execute('''
-                UPDATE consumption
-                SET count = count + :count
-                WHERE user_id = :user_id AND product_id = :product_id
-                ''', {
-                    'user_id': user.id,
-                    'product_id': product.id,
-                    'count': count
-                })
-            # Make sure exactly one consumption row was updated/inserted.
-            affected = c.execute('SELECT changes()').fetchone()[0]
-            if affected != 1:
-                raise DatabaseConsistencyError(
-                    f'increment_consumption should affect 1 consumption row, but affected {affected}')
-            # Compute the cost of the transaction and subtract it from the user's account balance.
+            # Subtract the price from the user's account balance.
             c.execute('''
             UPDATE users
             SET balance = balance - :cost
             WHERE user_id = :user_id''', {
                 'user_id': user.id,
-                'cost': count * product.price_member if user.is_member else count * product.price_non_member
+                'cost': price
             })
             # Make sure exactly one user row was updated.
             affected = c.execute('SELECT changes()').fetchone()[0]
@@ -474,11 +472,10 @@ class MatematDatabase(object):
             # Subtract the number of purchased units from the product's stock.
             c.execute('''
             UPDATE products
-            SET stock = stock - :count
+            SET stock = stock - 1
             WHERE product_id = :product_id
             ''', {
                 'product_id': product.id,
-                'count': count
             })
             # Make sure exactly one product row was updated.
             affected = c.execute('SELECT changes()').fetchone()[0]
@@ -509,6 +506,7 @@ class MatematDatabase(object):
     def deposit(self, user: User, amount: int) -> None:
         """
         Update the account balance of a user.
+
         :param user: The user to update the account balance for.
         :param amount: The amount to add to the account balance.
         :raises DatabaseConsistencyError: If the user represented by the object does not exist.
@@ -516,6 +514,18 @@ class MatematDatabase(object):
         if amount < 0:
             raise ValueError('Cannot deposit a negative value')
         with self.db.transaction() as c:
+            c.execute('''
+            INSERT INTO transactions (user_id, value, old_balance)
+              VALUES (:user_id, :value, :old_balance)
+            ''', {
+                'user_id': user.id,
+                'value': amount,
+                'old_balance': user.balance
+            })
+            c.execute('''
+            INSERT INTO deposits (ta_id)
+              VALUES (last_insert_rowid())
+            ''')
             c.execute('''
             UPDATE users
             SET balance = balance + :amount
diff --git a/matemat/db/migrations.py b/matemat/db/migrations.py
new file mode 100644
index 0000000..28274d6
--- /dev/null
+++ b/matemat/db/migrations.py
@@ -0,0 +1,115 @@
+
+from typing import Dict
+
+import sqlite3
+
+
+def migrate_schema_1_to_2(c: sqlite3.Cursor):
+    # Create missing tables
+    c.execute('''
+        CREATE TABLE transactions (
+          ta_id INTEGER PRIMARY KEY,
+          user_id INTEGER NOT NULL,
+          value INTEGER(8) NOT NULL,
+          old_balance INTEGER(8) NOT NULL,
+          date INTEGER(8) DEFAULT (STRFTIME('%s', 'now')),
+          FOREIGN KEY (user_id) REFERENCES users(user_id)
+            ON DELETE CASCADE ON UPDATE CASCADE
+        );
+    ''')
+    c.execute('''
+        CREATE TABLE consumptions (
+          ta_id INTEGER PRIMARY KEY,
+          product_id INTEGER DEFAULT NULL,
+          FOREIGN KEY (ta_id) REFERENCES transactions(ta_id)
+            ON DELETE CASCADE ON UPDATE CASCADE,
+          FOREIGN KEY (product_id) REFERENCES products(product_id)
+            ON DELETE SET NULL ON UPDATE CASCADE
+        );
+    ''')
+    c.execute('''
+        CREATE TABLE deposits (
+          ta_id INTEGER PRIMARY KEY,
+          FOREIGN KEY (ta_id) REFERENCES transactions(ta_id)
+            ON DELETE CASCADE ON UPDATE CASCADE
+        );
+    ''')
+    c.execute('''
+        CREATE TABLE modifications (
+          ta_id INTEGER NOT NULL,
+          agent_id INTEGER NOT NULL,
+          reason TEXT DEFAULT NULL,
+          PRIMARY KEY (ta_id),
+          FOREIGN KEY (ta_id) REFERENCES transactions(ta_id)
+            ON DELETE CASCADE ON UPDATE CASCADE,
+          FOREIGN KEY (agent_id) REFERENCES users(user_id)
+            ON DELETE SET NULL ON UPDATE CASCADE
+        );
+    ''')
+
+    #
+    # Convert entries from the old consumption table into entries for the new consumptions table
+    #
+
+    # Fetch current users, their balance and membership status
+    c.execute('SELECT user_id, balance, is_member FROM users')
+    balances: Dict[int, int] = dict()
+    memberships: Dict[int, bool] = dict()
+    for user_id, balance, member in c:
+        balances[user_id] = balance
+        memberships[user_id] = bool(member)
+
+    # Fetch current products and their prices
+    c.execute('SELECT product_id, price_member, price_non_member FROM products')
+    prices_member: Dict[int, int] = dict()
+    prices_non_member: Dict[int, int] = dict()
+    for product_id, price_member, price_non_member in c:
+        prices_member[product_id] = price_member
+        prices_non_member[product_id] = price_non_member
+
+    # As the following migration does reverse insertions, compute the max. primary key that can occur, and
+    # further down count downward from there
+    c.execute('SELECT SUM(count) FROM consumption')
+    ta_id: int = c.fetchone()[0]
+
+    # Iterate (users x products)
+    for user_id in balances.keys():
+        member: bool = memberships[user_id]
+        for product_id in prices_member:
+            price: int = prices_member[product_id] if member else prices_non_member[product_id]
+
+            # Select the number of items the user has bought from this product
+            c.execute('''
+                SELECT consumption.count FROM consumption
+                  WHERE user_id = :user_id AND product_id = :product_id
+                ''', {
+                'user_id': user_id,
+                'product_id': product_id
+            })
+            row = c.fetchone()
+            if row is not None:
+                count: int = row[0]
+                # Insert one row per bought item, setting the date to NULL, as it is not known
+                for _ in range(count):
+                    # This migration "goes back in time", so after processing a purchase entry, "locally
+                    # refund" the payment to reconstruct the "older" entries
+                    balances[user_id] += price
+                    # Insert into base table
+                    c.execute('''
+                        INSERT INTO transactions (ta_id, user_id, value, old_balance, date)
+                          VALUES (:ta_id, :user_id, :value, :old_balance, NULL)
+                        ''', {
+                        'ta_id': ta_id,
+                        'user_id': user_id,
+                        'value': -price,
+                        'old_balance': balances[user_id]
+                    })
+                    # Insert into specialization table
+                    c.execute('INSERT INTO consumptions (ta_id, product_id) VALUES (:ta_id, :product_id)', {
+                        'ta_id': ta_id,
+                        'product_id': product_id
+                    })
+                    # Decrement the transaction table insertion primary key
+                    ta_id -= 1
+    # Drop the old consumption table
+    c.execute('DROP TABLE consumption')
diff --git a/matemat/db/schemas.py b/matemat/db/schemas.py
new file mode 100644
index 0000000..5434ec1
--- /dev/null
+++ b/matemat/db/schemas.py
@@ -0,0 +1,103 @@
+from typing import Dict, List
+
+SCHEMAS: Dict[int, List[str]] = dict()
+
+SCHEMAS[1] = [
+    '''
+    CREATE TABLE users (
+      user_id INTEGER PRIMARY KEY,
+      username TEXT UNIQUE NOT NULL,
+      email TEXT DEFAULT NULL,
+      password TEXT NOT NULL,
+      touchkey TEXT DEFAULT NULL,
+      is_admin INTEGER(1) NOT NULL DEFAULT 0,
+      is_member INTEGER(1) NOT NULL DEFAULT 1,
+      balance INTEGER(8) NOT NULL DEFAULT 0,
+      lastchange INTEGER(8) NOT NULL DEFAULT 0
+    );
+    ''',
+    '''
+    CREATE TABLE products (
+      product_id INTEGER PRIMARY KEY,
+      name TEXT UNIQUE NOT NULL,
+      stock INTEGER(8) NOT NULL DEFAULT 0,
+      price_member INTEGER(8) NOT NULL,
+      price_non_member INTEGER(8) NOT NULL
+    );
+    ''',
+    '''
+    CREATE TABLE consumption (
+      user_id INTEGER NOT NULL,
+      product_id INTEGER NOT NULL,
+      count INTEGER(8) NOT NULL DEFAULT 0,
+      PRIMARY KEY (user_id, product_id),
+      FOREIGN KEY (user_id) REFERENCES users(user_id)
+        ON DELETE CASCADE ON UPDATE CASCADE,
+      FOREIGN KEY (product_id) REFERENCES products(product_id)
+        ON DELETE CASCADE ON UPDATE CASCADE
+    );
+    ''']
+
+SCHEMAS[2] = [
+    '''
+    CREATE TABLE users (
+      user_id INTEGER PRIMARY KEY,
+      username TEXT UNIQUE NOT NULL,
+      email TEXT DEFAULT NULL,
+      password TEXT NOT NULL,
+      touchkey TEXT DEFAULT NULL,
+      is_admin INTEGER(1) NOT NULL DEFAULT 0,
+      is_member INTEGER(1) NOT NULL DEFAULT 1,
+      balance INTEGER(8) NOT NULL DEFAULT 0,
+      lastchange INTEGER(8) NOT NULL DEFAULT 0
+    );
+    ''',
+    '''
+    CREATE TABLE products (
+      product_id INTEGER PRIMARY KEY,
+      name TEXT UNIQUE NOT NULL,
+      stock INTEGER(8) NOT NULL DEFAULT 0,
+      price_member INTEGER(8) NOT NULL,
+      price_non_member INTEGER(8) NOT NULL
+    );
+    ''',
+    '''
+    CREATE TABLE transactions (  -- "superclass" of the following 3 tables
+      ta_id INTEGER PRIMARY KEY,
+      user_id INTEGER NOT NULL,
+      value INTEGER(8) NOT NULL,
+      old_balance INTEGER(8) NOT NULL,
+      date INTEGER(8) DEFAULT (STRFTIME('%s', 'now')),
+      FOREIGN KEY (user_id) REFERENCES users(user_id)
+        ON DELETE CASCADE ON UPDATE CASCADE
+    );
+    ''',
+    '''
+    CREATE TABLE consumptions (  -- transactions involving buying a product
+      ta_id INTEGER PRIMARY KEY,
+      product_id INTEGER DEFAULT NULL,
+      FOREIGN KEY (ta_id) REFERENCES transactions(ta_id)
+        ON DELETE CASCADE ON UPDATE CASCADE,
+      FOREIGN KEY (product_id) REFERENCES products(product_id)
+        ON DELETE SET NULL ON UPDATE CASCADE
+    );
+    ''',
+    '''
+    CREATE TABLE deposits (  -- transactions involving depositing cash
+      ta_id INTEGER PRIMARY KEY,
+      FOREIGN KEY (ta_id) REFERENCES transactions(ta_id)
+        ON DELETE CASCADE ON UPDATE CASCADE
+    );
+    ''',
+    '''
+    CREATE TABLE modifications (  -- transactions involving balance modification by an admin
+      ta_id INTEGER NOT NULL,
+      agent_id INTEGER NOT NULL,
+      reason TEXT DEFAULT NULL,
+      PRIMARY KEY (ta_id),
+      FOREIGN KEY (ta_id) REFERENCES transactions(ta_id)
+        ON DELETE CASCADE ON UPDATE CASCADE,
+      FOREIGN KEY (agent_id) REFERENCES users(user_id)
+        ON DELETE CASCADE ON UPDATE CASCADE
+    );
+    ''']
diff --git a/matemat/db/test/test_facade.py b/matemat/db/test/test_facade.py
index d15fa64..04c0eb4 100644
--- a/matemat/db/test/test_facade.py
+++ b/matemat/db/test/test_facade.py
@@ -143,18 +143,23 @@ class DatabaseTest(unittest.TestCase):
 
     def test_change_user(self) -> None:
         with self.db as db:
+            agent = db.create_user('admin', 'supersecurepassword', 'admin@example.com', True, True)
             user = db.create_user('testuser', 'supersecurepassword', 'testuser@example.com', True, True)
-            user.email = 'newaddress@example.com'
-            user.is_admin = False
-            user.is_member = False
-            db.change_user(user)
-            checkuser = db.login('testuser', 'supersecurepassword')
-            self.assertEqual('newaddress@example.com', checkuser.email)
+            db.change_user(user, agent, email='newaddress@example.com', is_admin=False, is_member=False, balance=4200)
+            # Changes must be reflected in the passed user object
+            self.assertEqual('newaddress@example.com', user.email)
+            self.assertFalse(user.is_admin)
+            self.assertFalse(user.is_member)
+            self.assertEqual(4200, user.balance)
+            # Changes must be reflected in the database
+            checkuser = db.get_user(user.id)
+            self.assertEqual('newaddress@example.com', user.email)
             self.assertFalse(checkuser.is_admin)
             self.assertFalse(checkuser.is_member)
+            self.assertEqual(4200, checkuser.balance)
             user._user_id = -1
             with self.assertRaises(DatabaseConsistencyError):
-                db.change_user(user)
+                db.change_user(user, agent, is_member='True')
 
     def test_delete_user(self) -> None:
         with self.db as db:
@@ -221,14 +226,18 @@ class DatabaseTest(unittest.TestCase):
     def test_change_product(self) -> None:
         with self.db as db:
             product = db.create_product('Club Mate', 200, 200)
-            product.name = 'Flora Power Mate'
-            product.price_member = 150
-            product.price_non_member = 250
-            db.change_product(product)
-            checkproduct = db.list_products()[0]
+            db.change_product(product, name='Flora Power Mate', price_member=150, price_non_member=250, stock=42)
+            # Changes must be reflected in the passed object
+            self.assertEqual('Flora Power Mate', product.name)
+            self.assertEqual(150, product.price_member)
+            self.assertEqual(250, product.price_non_member)
+            self.assertEqual(42, product.stock)
+            # Changes must be reflected in the database
+            checkproduct = db.get_product(product.id)
             self.assertEqual('Flora Power Mate', checkproduct.name)
             self.assertEqual(150, checkproduct.price_member)
             self.assertEqual(250, checkproduct.price_non_member)
+            self.assertEqual(42, checkproduct.stock)
             product._product_id = -1
             with self.assertRaises(DatabaseConsistencyError):
                 db.change_product(product)
@@ -313,14 +322,14 @@ class DatabaseTest(unittest.TestCase):
             db.restock(fritzmate, 10)
 
             # user1 is somewhat addicted to caffeine
-            db.increment_consumption(user1, clubmate, 1)
-            db.increment_consumption(user1, clubmate, 2)
-            db.increment_consumption(user1, florapowermate, 3)
+            for _ in range(3):
+                db.increment_consumption(user1, clubmate)
+                db.increment_consumption(user1, florapowermate)
 
             # user2 is reeeally addicted
-            db.increment_consumption(user2, clubmate, 7)
-            db.increment_consumption(user2, florapowermate, 3)
-            db.increment_consumption(user2, florapowermate, 4)
+            for _ in range(7):
+                db.increment_consumption(user2, clubmate)
+                db.increment_consumption(user2, florapowermate)
 
             with db.transaction(exclusive=False) as c:
                 c.execute('''SELECT balance FROM users WHERE user_id = ?''', [user1.id])
diff --git a/matemat/db/test/test_migrations.py b/matemat/db/test/test_migrations.py
new file mode 100644
index 0000000..0488a96
--- /dev/null
+++ b/matemat/db/test/test_migrations.py
@@ -0,0 +1,124 @@
+
+import unittest
+
+import sqlite3
+
+from matemat.db import DatabaseWrapper
+from matemat.db.schemas import SCHEMAS
+
+
+class TestMigrations(unittest.TestCase):
+
+    def setUp(self):
+        # Create an in-memory database for testing
+        self.db = DatabaseWrapper(':memory:')
+
+    def _initialize_db(self, schema_version: int):
+        self.db._sqlite_db = sqlite3.connect(':memory:')
+        cursor: sqlite3.Cursor = self.db._sqlite_db.cursor()
+        cursor.execute('BEGIN EXCLUSIVE')
+        for cmd in SCHEMAS[schema_version]:
+            cursor.execute(cmd)
+        cursor.execute('COMMIT')
+
+    def test_downgrade_fail(self):
+        # Test that downgrades are forbidden
+        self.db.SCHEMA_VERSION = 1
+        self.db._sqlite_db = sqlite3.connect(':memory:')
+        self.db._sqlite_db.execute('PRAGMA user_version = 2')
+        with self.assertRaises(RuntimeError):
+            with self.db:
+                pass
+
+    def test_upgrade_1_to_2(self):
+        # Setup test db with example entries covering - hopefully - all cases
+        self._initialize_db(1)
+        cursor: sqlite3.Cursor = self.db._sqlite_db.cursor()
+        cursor.execute('''
+            INSERT INTO users VALUES
+              (1, 'testadmin', 'a@b.c', '$2a$10$herebehashes', NULL, 1, 1, 1337, 0),
+              (2, 'testuser', NULL, '$2a$10$herebehashes', '$2a$10$herebehashes', 0, 1, 4242, 0),
+              (3, 'alien', NULL, '$2a$10$herebehashes', '$2a$10$herebehashes', 0, 0, 1234, 0)
+            ''')
+        cursor.execute('''
+            INSERT INTO products VALUES
+              (1, 'Club Mate', 42, 200, 250),
+              (2, 'Flora Power Mate (1/4l)', 10, 100, 150)
+            ''')
+        cursor.execute('''
+            INSERT INTO consumption VALUES
+              (1, 1, 5), (1, 2, 3), (2, 2, 10), (3, 1, 3), (3, 2, 4)
+            ''')
+        cursor.execute('PRAGMA user_version = 1')
+
+        # Kick off the migration
+        self.db._setup()
+
+        # Test whether the new tables were created
+        cursor.execute('PRAGMA table_info(transactions)')
+        self.assertNotEqual(0, len(cursor.fetchall()))
+        cursor.execute('PRAGMA table_info(consumptions)')
+        self.assertNotEqual(0, len(cursor.fetchall()))
+        cursor.execute('PRAGMA table_info(deposits)')
+        self.assertNotEqual(0, len(cursor.fetchall()))
+        cursor.execute('PRAGMA table_info(modifications)')
+        self.assertNotEqual(0, len(cursor.fetchall()))
+        # Test whether the old consumption table was dropped
+        cursor.execute('PRAGMA table_info(consumption)')
+        self.assertEqual(0, len(cursor.fetchall()))
+
+        # Test number of entries in the new tables
+        cursor.execute('SELECT COUNT(ta_id) FROM transactions')
+        self.assertEqual(25, cursor.fetchone()[0])
+        cursor.execute('SELECT COUNT(ta_id) FROM consumptions')
+        self.assertEqual(25, cursor.fetchone()[0])
+        cursor.execute('SELECT COUNT(ta_id) FROM deposits')
+        self.assertEqual(0, cursor.fetchone()[0])
+        cursor.execute('SELECT COUNT(ta_id) FROM modifications')
+        self.assertEqual(0, cursor.fetchone()[0])
+
+        # The (user_id=2 x product_id=1) combination should never appear
+        cursor.execute('''
+            SELECT COUNT(t.ta_id)
+              FROM transactions AS t
+              LEFT JOIN consumptions AS c
+                ON t.ta_id = c.ta_id
+              WHERE t.user_id = 2 AND c.product_id = 1''')
+        self.assertEqual(0, cursor.fetchone()[0])
+
+        # Test that one entry per consumption was created, and their values match the negative price
+        cursor.execute('''
+            SELECT COUNT(t.ta_id)
+              FROM transactions AS t
+              LEFT JOIN consumptions AS c
+                ON t.ta_id = c.ta_id
+              WHERE t.user_id = 1 AND c.product_id = 1 AND t.value = -200''')
+        self.assertEqual(5, cursor.fetchone()[0])
+        cursor.execute('''
+            SELECT COUNT(t.ta_id)
+              FROM transactions AS t
+              LEFT JOIN consumptions AS c
+                ON t.ta_id = c.ta_id
+              WHERE t.user_id = 1 AND c.product_id = 2 AND t.value = -100''')
+        self.assertEqual(3, cursor.fetchone()[0])
+        cursor.execute('''
+            SELECT COUNT(t.ta_id)
+              FROM transactions AS t
+              LEFT JOIN consumptions AS c
+                ON t.ta_id = c.ta_id
+              WHERE t.user_id = 2 AND c.product_id = 2 AND t.value = -100''')
+        self.assertEqual(10, cursor.fetchone()[0])
+        cursor.execute('''
+            SELECT COUNT(t.ta_id)
+              FROM transactions AS t
+              LEFT JOIN consumptions AS c
+                ON t.ta_id = c.ta_id
+              WHERE t.user_id = 3 AND c.product_id = 1 AND t.value = -250''')
+        self.assertEqual(3, cursor.fetchone()[0])
+        cursor.execute('''
+            SELECT COUNT(t.ta_id)
+              FROM transactions AS t
+              LEFT JOIN consumptions AS c
+                ON t.ta_id = c.ta_id
+              WHERE t.user_id = 3 AND c.product_id = 2 AND t.value = -150''')
+        self.assertEqual(4, cursor.fetchone()[0])
diff --git a/matemat/db/test/test_wrapper.py b/matemat/db/test/test_wrapper.py
index e5a52c2..1b38f60 100644
--- a/matemat/db/test/test_wrapper.py
+++ b/matemat/db/test/test_wrapper.py
@@ -1,6 +1,8 @@
 
 import unittest
 
+import sqlite3
+
 from matemat.db import DatabaseWrapper
 
 
diff --git a/matemat/db/wrapper.py b/matemat/db/wrapper.py
index 34af430..c0cddc4 100644
--- a/matemat/db/wrapper.py
+++ b/matemat/db/wrapper.py
@@ -4,6 +4,8 @@ from typing import Any, Optional
 import sqlite3
 
 from matemat.exceptions import DatabaseConsistencyError
+from matemat.db.schemas import SCHEMAS
+from matemat.db.migrations import migrate_schema_1_to_2
 
 
 class Transaction(object):
@@ -39,38 +41,8 @@ class Transaction(object):
 
 
 class DatabaseWrapper(object):
-    SCHEMA_VERSION = 1
 
-    SCHEMA = '''
-    CREATE TABLE users (
-      user_id INTEGER PRIMARY KEY,
-      username TEXT UNIQUE NOT NULL,
-      email TEXT DEFAULT NULL,
-      password TEXT NOT NULL,
-      touchkey TEXT DEFAULT NULL,
-      is_admin INTEGER(1) NOT NULL DEFAULT 0,
-      is_member INTEGER(1) NOT NULL DEFAULT 1,
-      balance INTEGER(8) NOT NULL DEFAULT 0,
-      lastchange INTEGER(8) NOT NULL DEFAULT 0
-    );
-    CREATE TABLE products (
-      product_id INTEGER PRIMARY KEY,
-      name TEXT UNIQUE NOT NULL,
-      stock INTEGER(8) NOT NULL DEFAULT 0,
-      price_member INTEGER(8) NOT NULL,
-      price_non_member INTEGER(8) NOT NULL
-    );
-    CREATE TABLE consumption (
-      user_id INTEGER NOT NULL,
-      product_id INTEGER NOT NULL,
-      count INTEGER(8) NOT NULL DEFAULT 0,
-      PRIMARY KEY (user_id, product_id),
-      FOREIGN KEY (user_id) REFERENCES users(user_id)
-        ON DELETE CASCADE ON UPDATE CASCADE,
-      FOREIGN KEY (product_id) REFERENCES products(product_id)
-        ON DELETE CASCADE ON UPDATE CASCADE
-    );
-    '''
+    SCHEMA_VERSION = 2
 
     def __init__(self, filename: str) -> None:
         self._filename: str = filename
@@ -92,13 +64,20 @@ class DatabaseWrapper(object):
         with self.transaction() as c:
             version: int = self._user_version
             if version < 1:
-                c.executescript(self.SCHEMA)
+                # Don't use executescript, as it issues a COMMIT first
+                for command in SCHEMAS[self.SCHEMA_VERSION]:
+                    c.execute(command)
             elif version < self.SCHEMA_VERSION:
-                self._upgrade(old=version, new=self.SCHEMA_VERSION)
+                self._upgrade(from_version=version, to_version=self.SCHEMA_VERSION)
+            elif version > self.SCHEMA_VERSION:
+                raise RuntimeError('Database schema is newer than supported by this version of Matemat.')
             self._user_version = self.SCHEMA_VERSION
 
-    def _upgrade(self, old: int, new: int) -> None:
-        pass
+    def _upgrade(self, from_version: int, to_version: int) -> None:
+        with self.transaction() as c:
+            # Note to future s3lph: If there are further migrations, also consider upgrades like 1 -> 3
+            if from_version == 1 and to_version == 2:
+                migrate_schema_1_to_2(c)
 
     def connect(self) -> None:
         if self.is_connected():
diff --git a/matemat/webserver/pagelets/buy.py b/matemat/webserver/pagelets/buy.py
index 24ac60c..3b68cee 100644
--- a/matemat/webserver/pagelets/buy.py
+++ b/matemat/webserver/pagelets/buy.py
@@ -17,12 +17,8 @@ def buy(method: str,
     with MatematDatabase(config['DatabaseFile']) as db:
         uid: int = session_vars['authenticated_user']
         user = db.get_user(uid)
-        if 'n' in args:
-            n = int(str(args.n))
-        else:
-            n = 1
         if 'pid' in args:
             pid = int(str(args.pid))
             product = db.get_product(pid)
-            db.increment_consumption(user, product, n)
+            db.increment_consumption(user, product)
         return RedirectResponse('/')
diff --git a/matemat/webserver/test/abstract_httpd_test.py b/matemat/webserver/test/abstract_httpd_test.py
index 5680836..aadc346 100644
--- a/matemat/webserver/test/abstract_httpd_test.py
+++ b/matemat/webserver/test/abstract_httpd_test.py
@@ -119,10 +119,12 @@ class MockServer:
         # Set up logger
         self.logger: logging.Logger = logging.getLogger('matemat unit test')
         self.logger.setLevel(logging.DEBUG)
+        # Disable logging
+        self.logger.addHandler(logging.NullHandler())
         # Initalize a log handler to stderr and set the log format
-        sh: logging.StreamHandler = logging.StreamHandler()
-        sh.setFormatter(logging.Formatter('%(asctime)s %(name)s [%(levelname)s]: %(message)s'))
-        self.logger.addHandler(sh)
+        # sh: logging.StreamHandler = logging.StreamHandler()
+        # sh.setFormatter(logging.Formatter('%(asctime)s %(name)s [%(levelname)s]: %(message)s'))
+        # self.logger.addHandler(sh)
 
 
 class MockSocket(bytes):