1 files changed, 10 insertions, 0 deletions
diff --git a/sqlglot/dialects/dialect.py b/sqlglot/dialects/dialect.py
index 0c2beba..1b20e0a 100644
--- a/sqlglot/dialects/dialect.py
+++ b/sqlglot/dialects/dialect.py
@@ -122,9 +122,15 @@ class Dialect(metaclass=_Dialect):
     def get_or_raise(cls, dialect):
         if not dialect:
             return cls
+        if isinstance(dialect, _Dialect):
+            return dialect
+        if isinstance(dialect, Dialect):
+            return dialect.__class__
+
         result = cls.get(dialect)
         if not result:
             raise ValueError(f"Unknown dialect '{dialect}'")
+
         return result
 
     @classmethod
@@ -196,6 +202,10 @@ class Dialect(metaclass=_Dialect):
         )
 
 
+if t.TYPE_CHECKING:
+    DialectType = t.Union[str, Dialect, t.Type[Dialect], None]
+
+
 def rename_func(name):
     def _rename(self, expression):
         args = flatten(expression.args.values())