diff --git a/documentation20/webdocs/markdowndocs/connector-ch.md b/documentation20/webdocs/markdowndocs/connector-ch.md
index bcaabe3c0a..6736eea7c7 100644
--- a/documentation20/webdocs/markdowndocs/connector-ch.md
+++ b/documentation20/webdocs/markdowndocs/connector-ch.md
@@ -852,7 +852,7 @@ npm install td2.0-connector
 ### Linux
 
 - `python` (建议`v2.7` , `v3.x.x` 目前还不支持)
-- `node`  必须采用v10.x版本，其他版本存在包兼容性的问题。
+- `node`  2.0.6支持v12.x和v10.x，2.0.5及更早版本支持v10.x版本，其他版本可能存在包兼容性的问题。
 - `make`
 - c语言编译器比如<a href="https://gcc.gnu.org">GCC</a>
 
diff --git a/src/connector/python/linux/python2/setup.py b/src/connector/python/linux/python2/setup.py
index 2cad664307..dba234d7a4 100644
--- a/src/connector/python/linux/python2/setup.py
+++ b/src/connector/python/linux/python2/setup.py
@@ -5,7 +5,7 @@ with open("README.md", "r") as fh:
 
 setuptools.setup(
     name="taos",
-    version="2.0.4",
+    version="2.0.5",
     author="Taosdata Inc.",
     author_email="support@taosdata.com",
     description="TDengine python client package",
diff --git a/src/connector/python/linux/python2/taos/cursor.py b/src/connector/python/linux/python2/taos/cursor.py
index ada83d72c5..bc3b6c65d8 100644
--- a/src/connector/python/linux/python2/taos/cursor.py
+++ b/src/connector/python/linux/python2/taos/cursor.py
@@ -1,7 +1,6 @@
 from .cinterface import CTaosInterface
 from .error import *
 from .constants import FieldType
-import threading
 
 
 class TDengineCursor(object):
@@ -36,7 +35,6 @@ class TDengineCursor(object):
         self._block_iter = 0
         self._affected_rows = 0
         self._logfile = ""
-        self._threadId = threading.get_ident()
 
         if connection is not None:
             self._connection = connection
diff --git a/src/kit/taosdemox/taosdemox.c b/src/kit/taosdemox/taosdemox.c
index f2f7aaaf5d..40ca232327 100644
--- a/src/kit/taosdemox/taosdemox.c
+++ b/src/kit/taosdemox/taosdemox.c
@@ -93,6 +93,8 @@ extern char configDir[];
 #define   MAX_QUERY_SQL_COUNT    10
 #define   MAX_QUERY_SQL_LENGTH   256
 
+#define   MAX_DATABASE_COUNT     256
+
 typedef enum CREATE_SUB_TALBE_MOD_EN {
   PRE_CREATE_SUBTBL,
   AUTO_CREATE_SUBTBL,
@@ -116,7 +118,41 @@ enum QUERY_TYPE {
   INSERT_TYPE, 
   QUERY_TYPE_BUT
 } ;  
-  
+
+enum _show_db_index {
+  TSDB_SHOW_DB_NAME_INDEX,
+  TSDB_SHOW_DB_CREATED_TIME_INDEX,
+  TSDB_SHOW_DB_NTABLES_INDEX,
+  TSDB_SHOW_DB_VGROUPS_INDEX,
+  TSDB_SHOW_DB_REPLICA_INDEX,
+  TSDB_SHOW_DB_QUORUM_INDEX,  
+  TSDB_SHOW_DB_DAYS_INDEX,
+  TSDB_SHOW_DB_KEEP_INDEX,
+  TSDB_SHOW_DB_CACHE_INDEX,
+  TSDB_SHOW_DB_BLOCKS_INDEX,
+  TSDB_SHOW_DB_MINROWS_INDEX,
+  TSDB_SHOW_DB_MAXROWS_INDEX,
+  TSDB_SHOW_DB_WALLEVEL_INDEX,
+  TSDB_SHOW_DB_FSYNC_INDEX,
+  TSDB_SHOW_DB_COMP_INDEX,
+  TSDB_SHOW_DB_CACHELAST_INDEX,
+  TSDB_SHOW_DB_PRECISION_INDEX,  
+  TSDB_SHOW_DB_UPDATE_INDEX,
+  TSDB_SHOW_DB_STATUS_INDEX,
+  TSDB_MAX_SHOW_DB
+};
+
+// -----------------------------------------SHOW TABLES CONFIGURE -------------------------------------
+enum _show_stables_index {
+  TSDB_SHOW_STABLES_NAME_INDEX,
+  TSDB_SHOW_STABLES_CREATED_TIME_INDEX,
+  TSDB_SHOW_STABLES_COLUMNS_INDEX,
+  TSDB_SHOW_STABLES_METRIC_INDEX,  
+  TSDB_SHOW_STABLES_UID_INDEX,  
+  TSDB_SHOW_STABLES_TID_INDEX,
+  TSDB_SHOW_STABLES_VGID_INDEX,  
+  TSDB_MAX_SHOW_STABLES
+};  
 enum _describe_table_index {
   TSDB_DESCRIBE_METRIC_FIELD_INDEX,
   TSDB_DESCRIBE_METRIC_TYPE_INDEX,
@@ -219,6 +255,28 @@ typedef struct SSuperTable_S {
   int64_t    totalAffectedRows;
 } SSuperTable;
 
+typedef struct {
+  char     name[TSDB_DB_NAME_LEN + 1];
+  char     create_time[32];
+  int32_t  ntables;
+  int32_t  vgroups;  
+  int16_t  replica;
+  int16_t  quorum;
+  int16_t  days;  
+  char     keeplist[32];
+  int32_t  cache; //MB
+  int32_t  blocks;
+  int32_t  minrows;
+  int32_t  maxrows;
+  int8_t   wallevel;
+  int32_t  fsync;
+  int8_t   comp;
+  int8_t   cachelast;
+  char     precision[8];   // time resolution
+  int8_t   update;
+  char     status[16];
+} SDbInfo;
+
 typedef struct SDbCfg_S { 
 //  int       maxtablesPerVnode;
   int       minRows; 
@@ -1126,6 +1184,272 @@ static void printfQueryMeta() {
   printf("\033[1m\033[40;32m================ query.json parse result ================\033[0m\n");
 }
 
+
+static char* xFormatTimestamp(char* buf, int64_t val, int precision) {
+  time_t tt;
+  if (precision == TSDB_TIME_PRECISION_MICRO) {
+    tt = (time_t)(val / 1000000);
+  } else {
+    tt = (time_t)(val / 1000);
+  }
+
+/* comment out as it make testcases like select_with_tags.sim fail.
+  but in windows, this may cause the call to localtime crash if tt < 0,
+  need to find a better solution.
+  if (tt < 0) {
+    tt = 0;
+  }
+  */
+
+#ifdef WINDOWS
+  if (tt < 0) tt = 0;
+#endif
+
+  struct tm* ptm = localtime(&tt);
+  size_t pos = strftime(buf, 32, "%Y-%m-%d %H:%M:%S", ptm);
+
+  if (precision == TSDB_TIME_PRECISION_MICRO) {
+    sprintf(buf + pos, ".%06d", (int)(val % 1000000));
+  } else {
+    sprintf(buf + pos, ".%03d", (int)(val % 1000));
+  }
+
+  return buf;
+}
+
+static void xDumpFieldToFile(FILE* fp, const char* val, TAOS_FIELD* field, int32_t length, int precision) {
+  if (val == NULL) {
+    fprintf(fp, "%s", TSDB_DATA_NULL_STR);
+    return;
+  }
+
+  char buf[TSDB_MAX_BYTES_PER_ROW];
+  switch (field->type) {
+    case TSDB_DATA_TYPE_BOOL:
+      fprintf(fp, "%d", ((((int32_t)(*((char *)val))) == 1) ? 1 : 0));
+      break;
+    case TSDB_DATA_TYPE_TINYINT:
+      fprintf(fp, "%d", *((int8_t *)val));
+      break;
+    case TSDB_DATA_TYPE_SMALLINT:
+      fprintf(fp, "%d", *((int16_t *)val));
+      break;
+    case TSDB_DATA_TYPE_INT:
+      fprintf(fp, "%d", *((int32_t *)val));
+      break;
+    case TSDB_DATA_TYPE_BIGINT:
+      fprintf(fp, "%" PRId64, *((int64_t *)val));
+      break;
+    case TSDB_DATA_TYPE_FLOAT:
+      fprintf(fp, "%.5f", GET_FLOAT_VAL(val));
+      break;
+    case TSDB_DATA_TYPE_DOUBLE:
+      fprintf(fp, "%.9f", GET_DOUBLE_VAL(val));
+      break;
+    case TSDB_DATA_TYPE_BINARY:
+    case TSDB_DATA_TYPE_NCHAR:
+      memcpy(buf, val, length);
+      buf[length] = 0;
+      fprintf(fp, "\'%s\'", buf);
+      break;
+    case TSDB_DATA_TYPE_TIMESTAMP:
+      xFormatTimestamp(buf, *(int64_t*)val, precision);
+      fprintf(fp, "'%s'", buf);
+      break;
+    default:
+      break;
+  }
+}
+
+static int xDumpResultToFile(const char* fname, TAOS_RES* tres) {
+  TAOS_ROW row = taos_fetch_row(tres);
+  if (row == NULL) {
+    return 0;
+  }
+
+  FILE* fp = fopen(fname, "at");
+  if (fp == NULL) {
+    fprintf(stderr, "ERROR: failed to open file: %s\n", fname);
+    return -1;
+  }
+
+  int num_fields = taos_num_fields(tres);
+  TAOS_FIELD *fields = taos_fetch_fields(tres);
+  int precision = taos_result_precision(tres);
+
+  for (int col = 0; col < num_fields; col++) {
+    if (col > 0) {
+      fprintf(fp, ",");
+    }
+    fprintf(fp, "%s", fields[col].name);
+  }
+  fputc('\n', fp);
+  
+  int numOfRows = 0;
+  do {
+    int32_t* length = taos_fetch_lengths(tres);
+    for (int i = 0; i < num_fields; i++) {
+      if (i > 0) {
+        fputc(',', fp);
+      }
+      xDumpFieldToFile(fp, (const char*)row[i], fields +i, length[i], precision);
+    }
+    fputc('\n', fp);
+
+    numOfRows++;
+    row = taos_fetch_row(tres);
+  } while( row != NULL);
+
+  fclose(fp);
+
+  return numOfRows;
+}
+
+static int getDbFromServer(TAOS * taos, SDbInfo** dbInfos) {  
+  TAOS_RES * res;  
+  TAOS_ROW row = NULL;
+  int count = 0;
+  
+  res = taos_query(taos, "show databases;");  
+  int32_t code = taos_errno(res);
+  
+  if (code != 0) {
+    fprintf(stderr, "failed to run <show databases>, reason: %s\n", taos_errstr(res));
+    return -1;
+  }
+
+  TAOS_FIELD *fields = taos_fetch_fields(res);
+
+  while ((row = taos_fetch_row(res)) != NULL) {
+    // sys database name : 'log'
+    if (strncasecmp(row[TSDB_SHOW_DB_NAME_INDEX], "log", fields[TSDB_SHOW_DB_NAME_INDEX].bytes) == 0) continue;
+
+    dbInfos[count] = (SDbInfo *)calloc(1, sizeof(SDbInfo));
+    if (dbInfos[count] == NULL) {
+      fprintf(stderr, "failed to allocate memory for some dbInfo[%d]\n", count);
+      return -1;
+    }
+
+    strncpy(dbInfos[count]->name, (char *)row[TSDB_SHOW_DB_NAME_INDEX], fields[TSDB_SHOW_DB_NAME_INDEX].bytes);
+    xFormatTimestamp(dbInfos[count]->create_time, *(int64_t*)row[TSDB_SHOW_DB_CREATED_TIME_INDEX], TSDB_TIME_PRECISION_MILLI);
+    dbInfos[count]->ntables = *((int32_t *)row[TSDB_SHOW_DB_NTABLES_INDEX]);
+    dbInfos[count]->vgroups = *((int32_t *)row[TSDB_SHOW_DB_VGROUPS_INDEX]);  
+    dbInfos[count]->replica = *((int16_t *)row[TSDB_SHOW_DB_REPLICA_INDEX]);
+    dbInfos[count]->quorum = *((int16_t *)row[TSDB_SHOW_DB_QUORUM_INDEX]);
+    dbInfos[count]->days = *((int16_t *)row[TSDB_SHOW_DB_DAYS_INDEX]);  
+
+    strncpy(dbInfos[count]->keeplist, (char *)row[TSDB_SHOW_DB_KEEP_INDEX], fields[TSDB_SHOW_DB_KEEP_INDEX].bytes);      
+    dbInfos[count]->cache = *((int32_t *)row[TSDB_SHOW_DB_CACHE_INDEX]);
+    dbInfos[count]->blocks = *((int32_t *)row[TSDB_SHOW_DB_BLOCKS_INDEX]);
+    dbInfos[count]->minrows = *((int32_t *)row[TSDB_SHOW_DB_MINROWS_INDEX]);
+    dbInfos[count]->maxrows = *((int32_t *)row[TSDB_SHOW_DB_MAXROWS_INDEX]);
+    dbInfos[count]->wallevel = *((int8_t *)row[TSDB_SHOW_DB_WALLEVEL_INDEX]);
+    dbInfos[count]->fsync = *((int32_t *)row[TSDB_SHOW_DB_FSYNC_INDEX]);
+    dbInfos[count]->comp = (int8_t)(*((int8_t *)row[TSDB_SHOW_DB_COMP_INDEX]));
+    dbInfos[count]->cachelast = (int8_t)(*((int8_t *)row[TSDB_SHOW_DB_CACHELAST_INDEX]));
+
+    strncpy(dbInfos[count]->precision, (char *)row[TSDB_SHOW_DB_PRECISION_INDEX], fields[TSDB_SHOW_DB_PRECISION_INDEX].bytes);  
+    dbInfos[count]->update = *((int8_t *)row[TSDB_SHOW_DB_UPDATE_INDEX]);
+    strncpy(dbInfos[count]->status, (char *)row[TSDB_SHOW_DB_STATUS_INDEX], fields[TSDB_SHOW_DB_STATUS_INDEX].bytes); 
+    
+    count++;
+    if (count > MAX_DATABASE_COUNT) {
+      fprintf(stderr, "The database count overflow than %d\n", MAX_DATABASE_COUNT);      
+      break;
+    }
+  }
+
+  return count;
+}
+
+static void printfDbInfoForQueryToFile(char* filename, SDbInfo* dbInfos, int index) {
+  FILE *fp = NULL;
+  if (filename[0] != 0) {
+    fp = fopen(filename, "at");
+    if (fp == NULL) {
+      fprintf(stderr, "failed to open file: %s\n", filename);
+      return;
+    }
+  }
+
+  fprintf(fp, "================ database[%d] ================\n", index);
+  fprintf(fp, "name: %s\n", dbInfos->name);
+  fprintf(fp, "created_time: %s\n", dbInfos->create_time);
+  fprintf(fp, "ntables: %d\n", dbInfos->ntables);
+  fprintf(fp, "vgroups: %d\n", dbInfos->vgroups);  
+  fprintf(fp, "replica: %d\n", dbInfos->replica);
+  fprintf(fp, "quorum: %d\n", dbInfos->quorum);
+  fprintf(fp, "days: %d\n", dbInfos->days);    
+  fprintf(fp, "keep1,keep2,keep(D): %s\n", dbInfos->keeplist);      
+  fprintf(fp, "cache(MB): %d\n", dbInfos->cache);
+  fprintf(fp, "blocks: %d\n", dbInfos->blocks);
+  fprintf(fp, "minrows: %d\n", dbInfos->minrows);
+  fprintf(fp, "maxrows: %d\n", dbInfos->maxrows);
+  fprintf(fp, "wallevel: %d\n", dbInfos->wallevel);
+  fprintf(fp, "fsync: %d\n", dbInfos->fsync);
+  fprintf(fp, "comp: %d\n", dbInfos->comp);
+  fprintf(fp, "cachelast: %d\n", dbInfos->cachelast);  
+  fprintf(fp, "precision: %s\n", dbInfos->precision);  
+  fprintf(fp, "update: %d\n", dbInfos->update);
+  fprintf(fp, "status: %s\n", dbInfos->status); 
+  fprintf(fp, "\n");
+
+  fclose(fp);
+}
+
+static void printfQuerySystemInfo(TAOS * taos) {
+  char filename[MAX_QUERY_SQL_LENGTH+1] = {0};
+  char buffer[MAX_QUERY_SQL_LENGTH+1] = {0};
+  TAOS_RES* res;
+
+  time_t t;
+  struct tm* lt;
+  time(&t);
+  lt = localtime(&t);
+  snprintf(filename, MAX_QUERY_SQL_LENGTH, "querySystemInfo-%d-%d-%d %d:%d:%d", lt->tm_year+1900, lt->tm_mon, lt->tm_mday, lt->tm_hour, lt->tm_min, lt->tm_sec);
+  
+  // show variables
+  res = taos_query(taos, "show variables;");
+  //getResult(res, filename);
+  xDumpResultToFile(filename, res);
+
+  // show dnodes
+  res = taos_query(taos, "show dnodes;");
+  xDumpResultToFile(filename, res);
+  //getResult(res, filename);
+  
+  // show databases
+  res = taos_query(taos, "show databases;");
+  SDbInfo** dbInfos = (SDbInfo **)calloc(MAX_DATABASE_COUNT, sizeof(SDbInfo *));
+  if (dbInfos == NULL) {
+    fprintf(stderr, "failed to allocate memory\n");
+    return;
+  }
+  int dbCount = getDbFromServer(taos, dbInfos);
+  if (dbCount <= 0) return;
+
+  for (int i = 0; i < dbCount; i++) {
+    // printf database info 
+    printfDbInfoForQueryToFile(filename, dbInfos[i], i);
+    
+    // show db.vgroups
+    snprintf(buffer, MAX_QUERY_SQL_LENGTH, "show %s.vgroups;", dbInfos[i]->name);
+    res = taos_query(taos, buffer);
+    xDumpResultToFile(filename, res);
+  
+    // show db.stables
+    snprintf(buffer, MAX_QUERY_SQL_LENGTH, "show %s.stables;", dbInfos[i]->name);
+    res = taos_query(taos, buffer);
+    xDumpResultToFile(filename, res);
+
+    free(dbInfos[i]);
+  }
+
+  free(dbInfos);
+  
+}
+
+
 #ifdef TD_LOWA_CURL
 static size_t responseCallback(void *contents, size_t size, size_t nmemb, void *userp)
 {
@@ -4134,7 +4458,7 @@ void *subQueryProcess(void *sarg) {
 int queryTestProcess() {
   TAOS * taos = NULL;  
   taos_init();
-  taos = taos_connect(g_queryInfo.host, g_queryInfo.user, g_queryInfo.password, g_queryInfo.dbName, g_queryInfo.port);
+  taos = taos_connect(g_queryInfo.host, g_queryInfo.user, g_queryInfo.password, NULL, g_queryInfo.port);
   if (taos == NULL) {
     fprintf(stderr, "Failed to connect to TDengine, reason:%s\n", taos_errstr(NULL));
     exit(-1);
@@ -4147,6 +4471,8 @@ int queryTestProcess() {
   printfQueryMeta();
   printf("Press enter key to continue\n\n");
   (void)getchar();
+
+  printfQuerySystemInfo(taos);
   
   pthread_t  *pids  = NULL;
   threadInfo *infos = NULL;
diff --git a/src/mnode/src/mnodeTable.c b/src/mnode/src/mnodeTable.c
index deba859f94..7f463899ce 100644
--- a/src/mnode/src/mnodeTable.c
+++ b/src/mnode/src/mnodeTable.c
@@ -1081,20 +1081,13 @@ static int32_t mnodeDropSuperTableCb(SMnodeMsg *pMsg, int32_t code) {
   SSTableObj *pTable = (SSTableObj *)pMsg->pTable;
   if (code != TSDB_CODE_SUCCESS) {
     mError("msg:%p, app:%p stable:%s, failed to drop, sdb error", pMsg, pMsg->rpcMsg.ahandle, pTable->info.tableId);
-  } else {
-    mLInfo("msg:%p, app:%p stable:%s, is dropped from sdb", pMsg, pMsg->rpcMsg.ahandle, pTable->info.tableId);
+
+    return code;
   }
 
-  return code;
-}
-
-static int32_t mnodeProcessDropSuperTableMsg(SMnodeMsg *pMsg) {
-  if (pMsg == NULL) return TSDB_CODE_MND_APP_ERROR;
+  mLInfo("msg:%p, app:%p stable:%s, is dropped from sdb", pMsg, pMsg->rpcMsg.ahandle, pTable->info.tableId);
 
   SSTableObj *pStable = (SSTableObj *)pMsg->pTable;
-  mInfo("msg:%p, app:%p stable:%s will be dropped, hash:%p sizeOfVgList:%d", pMsg, pMsg->rpcMsg.ahandle,
-        pStable->info.tableId, pStable->vgHash, taosHashGetSize(pStable->vgHash));
-
   if (pStable->vgHash != NULL /*pStable->numOfTables != 0*/) {
     int32_t *pVgId = taosHashIterate(pStable->vgHash, NULL);
     while (pVgId) {
@@ -1122,6 +1115,16 @@ static int32_t mnodeProcessDropSuperTableMsg(SMnodeMsg *pMsg) {
     mnodeDropAllChildTablesInStable(pStable);
   }
 
+  return TSDB_CODE_SUCCESS;
+}
+
+static int32_t mnodeProcessDropSuperTableMsg(SMnodeMsg *pMsg) {
+  if (pMsg == NULL) return TSDB_CODE_MND_APP_ERROR;
+
+  SSTableObj *pStable = (SSTableObj *)pMsg->pTable;
+  mInfo("msg:%p, app:%p stable:%s will be dropped, hash:%p sizeOfVgList:%d", pMsg, pMsg->rpcMsg.ahandle,
+        pStable->info.tableId, pStable->vgHash, taosHashGetSize(pStable->vgHash));
+
   SSdbRow row = {
     .type    = SDB_OPER_GLOBAL,
     .pTable  = tsSuperTableSdb,
diff --git a/src/util/src/ttimer.c b/src/util/src/ttimer.c
index 809b69e8ad..9833449777 100644
--- a/src/util/src/ttimer.c
+++ b/src/util/src/ttimer.c
@@ -188,11 +188,7 @@ static void removeTimer(uintptr_t id) {
 }
 
 static int64_t getMonotonicMs(void) {
-#ifdef WINDOWS
   return (int64_t) getMonotonicUs() / 1000;
-#else
-  return taosGetTimestampMs();
-#endif
 }
 
 static void addToWheel(tmr_obj_t* timer, uint32_t delay) {
diff --git a/tests/pytest/functions/function_stddev_td2555.py b/tests/pytest/functions/function_stddev_td2555.py
new file mode 100644
index 0000000000..a4da7d5e29
--- /dev/null
+++ b/tests/pytest/functions/function_stddev_td2555.py
@@ -0,0 +1,91 @@
+###################################################################
+#           Copyright (c) 2016 by TAOS Technologies, Inc.
+#                     All rights reserved.
+#
+#  This file is proprietary and confidential to TAOS Technologies.
+#  No part of this file may be reproduced, stored, transmitted,
+#  disclosed or used in any form or by any means other than as
+#  expressly provided by the written permission from Jianhui Tao
+#
+###################################################################
+
+# -*- coding: utf-8 -*-
+
+import sys
+import taos
+from util.log import *
+from util.cases import *
+from util.sql import *
+import numpy as np
+
+
+class TDTestCase:
+    def init(self, conn, logSql):
+        tdLog.debug("start to execute %s" % __file__)
+        tdSql.init(conn.cursor())
+
+        self.rowNum = 100
+        self.ts = 1537146000000
+        self.clist1 = []
+        self.clist2 = []
+        self.clist3 = []
+        self.clist4 = []
+        self.clist5 = []
+        self.clist6 = []
+    
+    def getData(self):
+        for i in range(tdSql.queryRows):
+            for j in range(6):
+                exec('self.clist{}.append(tdSql.queryResult[i][j+1])'.format(j+1))
+        
+    def run(self):
+        tdSql.prepare()
+
+        tdSql.execute('''create table test(ts timestamp, col1 tinyint, col2 smallint, col3 int, col4 bigint, col5 float, col6 double, 
+                    col7 bool, col8 binary(20), col9 nchar(20)) tags(cid int,gbid binary(20),loc nchar(20))''')
+        tdSql.execute("create table test1 using test tags(1,'beijing','北京')")
+        tdSql.execute("create table test2 using test tags(2,'shanghai','深圳')")
+        tdSql.execute("create table test3 using test tags(2,'shenzhen','深圳')")
+        tdSql.execute("create table test4 using test tags(1,'shanghai','上海')")
+        for j in range(4):
+            for i in range(self.rowNum):
+                tdSql.execute("insert into test%d values(now-%dh, %d, %d, %d, %d, %f, %f, %d, 'taosdata%d', '涛思数据%d')" 
+                            % (j+1,i, i + 1, i + 1, i + 1, i + 1, i + i * 0.1, i * 1.5, i % 2, i + 1, i + 1))                      
+
+        # stddev verifacation 
+        tdSql.error("select stddev(ts) from test")
+        tdSql.error("select stddev(col7) from test")
+        tdSql.error("select stddev(col8) from test")
+        tdSql.error("select stddev(col9) from test")
+
+        con_list = [
+            ' where cid = 1 and ts >=now - 1d and ts <now',
+            " where gbid = 'beijing' and ts >=now - 1d and ts <now",                       
+            ' '
+        ]
+        for condition in con_list:
+            tdSql.query("select * from test %s"%(condition))
+            self.getData()
+            for i in range(6):
+                exec('tdSql.query("select stddev(col{}) from test {}")'.format(i+1,condition))
+                exec('tdSql.checkData(0, 0, np.std(self.clist{}))'.format(i+1))
+                exec('self.clist{}.clear()'.format(i+1))
+        print('step 2')
+        con_group_list = {
+            ' cid = 2 and ts >=now - 1d and ts <now group by tbname':2,
+             " loc = '深圳' and ts >=now - 1d and ts <now group by tbname " :2 ,
+             " gbid = 'shanghai' and ts >=now - 1d and ts <now group by cid " :2
+        }
+        result = [6.922186552,6.922186552,6.922186552,6.922186552,7.614405212,10.383279829]
+        for key,value in con_group_list.items():
+            for i in range(6):
+                    exec('tdSql.query("select stddev(col{}) from test where {}")'.format(i+1,key))
+                    for j in range(value):
+                        tdSql.checkData(j, 0, result[i])
+                      
+    def stop(self):
+        tdSql.close()
+        tdLog.success("%s successfully executed" % __file__)
+
+tdCases.addWindows(__file__, TDTestCase())
+tdCases.addLinux(__file__, TDTestCase())