diff --git a/pytest_examples/magic_post.py b/pytest_examples/magic_post.py
index c843f29..2947afa 100644
--- a/pytest_examples/magic_post.py
+++ b/pytest_examples/magic_post.py
@@ -1,7 +1,10 @@
 # this is the changed file
+from pydal import DAL
 
 my_method = SomeClass()['first']
 
+db = DAL("sqlite://my_real_database")
+
 db.define_table(
     "person",
     Field(
@@ -16,4 +19,9 @@
 
 db.define_table("empty")
 
-db_type = "sqlite"
+
+db.define_table("new_table",
+                Field("new_field")
+                )
+
+db_type = "psql"
diff --git a/pytest_examples/magic_pre.py b/pytest_examples/magic_pre.py
index 254ab57..bf09169 100644
--- a/pytest_examples/magic_pre.py
+++ b/pytest_examples/magic_pre.py
@@ -11,8 +11,13 @@
         default=my_method.new_uuid()
     ),
     Field("birthday", "datetime", default=datetime.datetime.utcnow()),
+    Field("removed")
 )
 
+db.define_table("old_table",
+                Field("old_field")
+                )
+
 db.define_table("empty")
 
-db_type = "sqlite"
\ No newline at end of file
+db_type = "psql"
diff --git a/src/pydal2sql/cli.py b/src/pydal2sql/cli.py
index 43b70bc..5c61397 100644
--- a/src/pydal2sql/cli.py
+++ b/src/pydal2sql/cli.py
@@ -5,6 +5,7 @@
 from typing import Annotated, Optional
 
 import typer
+from configuraptor import Singleton
 from rich import print
 from typer import Argument
 from typing_extensions import Never
@@ -16,7 +17,7 @@
     find_git_root,
     get_absolute_path_info,
     get_file_for_version,
-    handle_cli_create,
+    handle_cli,
 )
 from .typer_support import (
     DEFAULT_VERBOSITY,
@@ -101,7 +102,8 @@ def create(
 
     text = get_file_for_version(file_absolute_path, file_version, prompt_description="table definition")
 
-    return handle_cli_create(
+    return handle_cli(
+        "",
         text,
         db_type=db_type.value if db_type else None,
         tables=config.tables,
@@ -117,6 +119,12 @@ def alter(
     filename_before: OptionalArgument[str] = None,
     filename_after: OptionalArgument[str] = None,
     db_type: DB_Types = None,
+    tables: Annotated[
+        Optional[list[str]],
+        typer.Option("--table", "--tables", "-t", help="One or more table names, default is all tables."),
+    ] = None,
+    magic: Optional[bool] = None,
+    noop: Optional[bool] = None,
 ) -> bool:
     """
     Todo: docs
@@ -137,6 +145,8 @@ def alter(
     """
     git_root = find_git_root() or Path(os.getcwd())
 
+    config = state.update_config(magic=magic, noop=noop, tables=tables)
+
     before, after = extract_file_versions_and_paths(filename_before, filename_after)
 
     version_before, filename_before = before
@@ -150,7 +160,8 @@ def alter(
     if not (before_exists and after_exists):
         message = ""
         message += "" if before_exists else f"Path {filename_before} does not exist! "
-        message += "" if after_exists else f"Path {filename_after} does not exist!"
+        if filename_before != filename_after:
+            message += "" if after_exists else f"Path {filename_after} does not exist!"
         raise ValueError(message)
 
     code_before = get_file_for_version(
@@ -167,8 +178,15 @@ def alter(
     if code_before == code_after:
         raise ValueError("Both contain the same code!")
 
-    print(len(code_before), len(code_after), db_type)
-    return True
+    return handle_cli(
+        code_before,
+        code_after,
+        db_type=db_type.value if db_type else None,
+        tables=config.tables,
+        verbose=state.verbosity > Verbosity.normal,
+        noop=config.noop,
+        magic=config.magic,
+    )
 
 
 """
@@ -226,6 +244,11 @@ def main(
         version: display current version?
 
     """
+    if state.config:
+        # if a config already exists, it's outdated, so we clear it.
+        # only really applicable in Pytest scenarios where multiple commands are executed after eachother
+        Singleton.clear(state.config)
+
     state.load_config(config_file=config, verbosity=verbosity)
 
     if show_config:
diff --git a/src/pydal2sql/cli_support.py b/src/pydal2sql/cli_support.py
index 96761cc..791bed6 100644
--- a/src/pydal2sql/cli_support.py
+++ b/src/pydal2sql/cli_support.py
@@ -19,7 +19,12 @@
 from git.repo import Repo
 
 from .helpers import flatten
-from .magic import find_missing_variables, generate_magic_code
+from .magic import (
+    find_defined_variables,
+    find_missing_variables,
+    generate_magic_code,
+    remove_specific_variables,
+)
 
 
 def has_stdin_data() -> bool:  # pragma: no cover
@@ -153,7 +158,12 @@ def extract_file_version_and_path(
 def extract_file_versions_and_paths(
     filename_before: Optional[str], filename_after: Optional[str]
 ) -> tuple[tuple[str, str | None], tuple[str, str | None]]:
-    version_before, filepath_before = extract_file_version_and_path(filename_before, default_version="latest")
+    version_before, filepath_before = extract_file_version_and_path(
+        filename_before,
+        default_version="current"
+        if filename_after and filename_before and filename_after != filename_before
+        else "latest",
+    )
     version_after, filepath_after = extract_file_version_and_path(filename_after, default_version="current")
 
     if not (filepath_before or filepath_after):
@@ -192,8 +202,37 @@ def get_absolute_path_info(filename: Optional[str], version: str, git_root: Opti
     return exists, absolute_path
 
 
-def handle_cli_create(
-    code: str,
+def ensure_no_migrate_on_real_db(
+    code: str, db_names: typing.Iterable[str] = ("db", "database"), fix: typing.Optional[bool] = False
+) -> str:
+    variables = find_defined_variables(code)
+
+    found_variables = set()
+
+    for db_name in db_names:
+        if db_name in variables:
+            if fix:
+                code = remove_specific_variables(code, db_names)
+            else:
+                found_variables.add(db_name)
+
+    if found_variables:
+        if len(found_variables) == 1:
+            var = next(iter(found_variables))
+            message = f"Variable {var} defined in code! "
+        else:  # pragma: no cover
+            var = ", ".join(found_variables)
+            message = f"Variables {var} defined in code! "
+        raise ValueError(
+            f"{message} Please remove this or use --magic to prevent performing actual migrations on your database."
+        )
+
+    return code
+
+
+def handle_cli(
+    code_before: str,
+    code_after: str,
     db_type: Optional[str] = None,
     tables: Optional[list[str] | list[list[str]]] = None,
     verbose: Optional[bool] = False,
@@ -203,6 +242,8 @@ def handle_cli_create(
     """
     Handle user input.
     """
+    # todo: prefix (e.g. public.)
+
     to_execute = string.Template(
         textwrap.dedent(
             """
@@ -219,19 +260,46 @@ def handle_cli_create(
 
         $extra
 
-        $code
+        $code_before
+
+        db_old = db
+        db_new = db = database = DAL(None, migrate=False)
+
+        $code_after
+
+        if not tables:
+            tables = set(db_old._tables + db_new._tables)
 
         if not tables:
-            tables = db._tables
+            print("No tables found!", file=sys.stderr)
+            print("Please use `db.define_table` or `database.define_table`, \
+            or if you really need to use an alias like my_db.define_tables, \
+            add `my_db = db` at the top of the file or pass `--db-name mydb`.")
+
 
         for table in tables:
-            print(generate_sql(db[table], db_type=db_type))
+            print('--', table)
+            if table in db_old and table in db_new:
+                print(generate_sql(db_old[table], db_new[table], db_type=db_type))
+            elif table in db_old:
+                print(f'DROP TABLE {table};')
+            else:
+                print(generate_sql(db_new[table], db_type=db_type))
     """
         )
     )
 
+    code_before = ensure_no_migrate_on_real_db(code_before, fix=magic)
+    code_after = ensure_no_migrate_on_real_db(code_after, fix=magic)
+
     generated_code = to_execute.substitute(
-        {"tables": flatten(tables or []), "db_type": db_type or "", "code": textwrap.dedent(code), "extra": ""}
+        {
+            "tables": flatten(tables or []),
+            "db_type": db_type or "",
+            "code_before": textwrap.dedent(code_before),
+            "code_after": textwrap.dedent(code_after),
+            "extra": "",
+        }
     )
     if verbose or noop:
         rich.print(generated_code, file=sys.stderr)
@@ -255,7 +323,8 @@ def handle_cli_create(
                     "tables": flatten(tables or []),
                     "db_type": db_type or "",
                     "extra": extra_code,
-                    "code": textwrap.dedent(code),
+                    "code_before": textwrap.dedent(code_before),
+                    "code_after": textwrap.dedent(code_after),
                 }
             )
 
diff --git a/src/pydal2sql/core.py b/src/pydal2sql/core.py
index 16ef09a..f9f2535 100644
--- a/src/pydal2sql/core.py
+++ b/src/pydal2sql/core.py
@@ -170,6 +170,10 @@ def generate_alter_statement(
                 fake_migrate=True,
             )
 
+            if not sql_log.exists():
+                # no changes!
+                return ""
+
             with sql_log.open() as f:
                 for line in f:
                     if not line.startswith(("ALTER", "UPDATE")):
diff --git a/src/pydal2sql/magic.py b/src/pydal2sql/magic.py
index 3c63746..431d080 100644
--- a/src/pydal2sql/magic.py
+++ b/src/pydal2sql/magic.py
@@ -20,6 +20,61 @@ def traverse_ast(node: ast.AST, variable_collector: typing.Callable[[ast.AST], N
         traverse_ast(child, variable_collector)
 
 
+def find_defined_variables(code_str: str) -> set[str]:
+    tree: ast.Module = ast.parse(code_str)
+
+    variables: set[str] = set()
+
+    def collect_definitions(node: ast.AST) -> None:
+        if isinstance(node, ast.Assign):
+            node_targets = typing.cast(list[ast.Name], node.targets)
+
+            variables.update(target.id for target in node_targets)
+
+    traverse_ast(tree, collect_definitions)
+    return variables
+
+
+def remove_specific_variables(code: str, to_remove: typing.Iterable[str] = ("db", "database")) -> str:
+    # Parse the code into an Abstract Syntax Tree (AST) - by ChatGPT
+    tree = ast.parse(code)
+
+    # Function to check if a variable name is 'db' or 'database'
+    def should_remove(var_name: str) -> bool:
+        return var_name in to_remove
+
+    # Function to recursively traverse the AST and remove definitions of 'db' or 'database'
+    def remove_db_and_database_defs_rec(node: ast.AST) -> typing.Optional[ast.AST]:
+        if isinstance(node, ast.Assign):
+            # Check if the assignment targets contain 'db' or 'database'
+            new_targets = [
+                target for target in node.targets if not (isinstance(target, ast.Name) and should_remove(target.id))
+            ]
+            node.targets = new_targets
+
+        elif isinstance(node, (ast.FunctionDef, ast.ClassDef)) and should_remove(node.name):
+            # Check if function or class name is 'db' or 'database'
+            return None
+
+        for child_node in ast.iter_child_nodes(node):
+            # Recursively process child nodes
+            new_child_node = remove_db_and_database_defs_rec(child_node)
+            if new_child_node is None and hasattr(node, "body"):
+                # If the child node was removed, remove it from the parent's body
+                node.body.remove(child_node)
+
+        return node
+
+    # Traverse the AST to remove 'db' and 'database' definitions
+    new_tree = remove_db_and_database_defs_rec(tree)
+
+    if not new_tree:  # pragma: no cover
+        return ""
+
+    # Generate the modified code from the new AST
+    return ast.unparse(new_tree)
+
+
 def find_variables(code_str: str) -> tuple[set[str], set[str]]:
     """
     Look through the source code in code_str and try to detect using ast parsing which variables are undefined.
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 31ac9ee..779922f 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -18,11 +18,16 @@ def test_cli_create():
         assert result.exit_code == 1
         assert "could not be found" in result.stderr
 
-        result = runner.invoke(app, ["create", "magic.py"])
+        result = runner.invoke(app, ["create", "magic.py@latest"])
         assert result.exit_code == 1
         assert not result.stdout
         assert "missing some variables" in result.stderr
 
+        result = runner.invoke(app, ["create", "magic.py@current"])
+        assert result.exit_code == 1
+        assert not result.stdout
+        assert "db defined in code!" in result.stderr
+
         result = runner.invoke(app, ["create", "magic.py", "--magic"])
         assert result.exit_code == 0
         assert not result.stderr
@@ -42,9 +47,11 @@ def test_cli_create():
 
 def test_cli_alter():
     with mock_git():
-        result = runner.invoke(app, ["alter", "missing.py"])
+        result = runner.invoke(app, ["alter", "missing.py", "missing2.py"])
         assert result.exit_code == 1
         assert "does not exist" in result.stderr
+        assert "missing.py" in result.stderr
+        assert "missing2.py" in result.stderr
 
         Path("empty.py").touch()
 
@@ -56,8 +63,13 @@ def test_cli_alter():
         assert result.exit_code == 1
         assert "contain the same code" in result.stderr
 
-        result = runner.invoke(app, ["alter", "magic.py"])
+        result = runner.invoke(app, ["alter", "magic.py", "--magic"])
+        print('++ stdout', result.stdout)
+        print('++ stderr', result.stderr)
         assert result.exit_code == 0
+        assert result.stdout
+
+
 
 def test_cli_version():
     result = runner.invoke(app, ["--version"])
diff --git a/tests/test_magic.py b/tests/test_magic.py
index c37c34f..93437f7 100644
--- a/tests/test_magic.py
+++ b/tests/test_magic.py
@@ -1,4 +1,6 @@
-from src.pydal2sql.magic import find_missing_variables, generate_magic_code
+import textwrap
+
+from src.pydal2sql.magic import find_missing_variables, generate_magic_code, remove_specific_variables
 
 
 def test_find_missing():
@@ -41,3 +43,18 @@ def test_fix_missing():
 
     assert "empty = Empty()" in code
     assert "bla = empty" in code
+
+def test_remove_specific_variables():
+    code = textwrap.dedent("""
+    db = 1
+    def database():
+        return True
+    
+    my_database = 'exists'
+    print('hi')
+    """)
+    new_code = remove_specific_variables(code)
+    assert "print('hi')" in new_code
+    assert 'db' not in new_code
+    assert 'def database' not in new_code
+    assert 'my_database' in new_code