disconnect and connect before running query

app.py

@@ -91,6 +91,7 @@ def testSQL(sql):
   if not isDataQuery(sql):
     return "Sorry not allowed to run. As the query modifies the data."
   try:
+    dbEngine.disconnect()
     dbEngine.connect()
     conn = dbEngine.getConnection()
     df = pd.read_sql_query(sql, con=conn)