format code

diff --git a/iotdb-client/client-py/iotdb/dbapi/Cursor.py b/iotdb-client/client-py/iotdb/dbapi/Cursor.py
index 018ade6..8897720 100644
--- a/iotdb-client/client-py/iotdb/dbapi/Cursor.py
+++ b/iotdb-client/client-py/iotdb/dbapi/Cursor.py

@@ -110,25 +110,6 @@
         else:
             sql = operation % parameters
 
-        time_index = []
-        time_names = []
-        if self.__sqlalchemy_mode:
-            sql_seqs = []
-            seqs = sql.split("\n")
-            for seq in seqs:
-                if seq.find("FROM Time Index") >= 0:
-                    time_index = [
-                        int(index)
-                        for index in seq.replace("FROM Time Index", "").split()
-                    ]
-                elif seq.find("FROM Time Name") >= 0:
-                    time_names = [
-                        name for name in seq.replace("FROM Time Name", "").split()
-                    ]
-                else:
-                    sql_seqs.append(seq)
-            sql = "\n".join(sql_seqs)
-
         data_set = self.__session.execute_statement(sql)
         col_names = None
         col_types = None
@@ -136,14 +117,6 @@
 
         if data_set:
             data = data_set.todf()
-
-            if self.__sqlalchemy_mode and time_index:
-                time_column = data.columns[0]
-                time_column_value = data.Time
-                del data[time_column]
-                for i in range(len(time_index)):
-                    data.insert(time_index[i], time_names[i], time_column_value)
-
             col_names = data.columns.tolist()
             col_types = data_set.get_column_types()
             rows = data.values.tolist()

diff --git a/iotdb-client/client-py/iotdb/sqlalchemy/IoTDBDialect.py b/iotdb-client/client-py/iotdb/sqlalchemy/IoTDBDialect.py
index 44f9e86..cc32649 100644
--- a/iotdb-client/client-py/iotdb/sqlalchemy/IoTDBDialect.py
+++ b/iotdb-client/client-py/iotdb/sqlalchemy/IoTDBDialect.py

@@ -37,7 +37,7 @@
     "INT32": types.Integer,
     "INT64": types.BigInteger,
     "FLOAT": types.Float,
-    "DOUBLE": types.Float,
+    "DOUBLE": types.Float(precision=53),
     "STRING": types.String,
     "TEXT": types.Text,
     "BLOB": types.LargeBinary,
@@ -86,7 +86,9 @@
     def create_connect_args(self, url):
         opts = url.translate_connect_args()
         opts.update(url.query)
+        opts["sqlalchemy_mode"] = True
         opts["sql_dialect"] = "table"
+        self._url_database = opts.get("database")
         return ([], opts)
 
     def initialize(self, connection):
@@ -96,7 +98,7 @@
         return None
 
     def _get_default_schema_name(self, connection):
-        return None
+        return getattr(self, "_url_database", None)
 
     def has_schema(self, connection, schema_name, **kw):
         return schema_name in self.get_schema_names(connection)
@@ -110,16 +112,20 @@
 
     def get_table_names(self, connection, schema=None, **kw):
         if schema:
-            connection.execute(text("USE %s" % schema))
-        cursor = connection.execute(text("SHOW TABLES"))
+            quoted = self.identifier_preparer.quote_identifier(schema)
+            cursor = connection.execute(text("SHOW TABLES FROM %s" % quoted))
+        else:
+            cursor = connection.execute(text("SHOW TABLES"))
         return [row[0] for row in cursor.fetchall()]
 
     def get_columns(self, connection, table_name, schema=None, **kw):
+        quoted_table = self.identifier_preparer.quote_identifier(table_name)
         if schema:
-            connection.execute(text("USE %s" % schema))
-        cursor = connection.execute(
-            text("SHOW COLUMNS FROM %s" % table_name)
-        )
+            quoted_schema = self.identifier_preparer.quote_identifier(schema)
+            qualified = "%s.%s" % (quoted_schema, quoted_table)
+        else:
+            qualified = quoted_table
+        cursor = connection.execute(text("DESC %s" % qualified))
         columns = []
         for row in cursor.fetchall():
             col_name = row[0]