diff --git a/tests/pytest/util/gettime.py b/tests/pytest/util/gettime.py
new file mode 100644
index 0000000000..94eed38478
--- /dev/null
+++ b/tests/pytest/util/gettime.py
@@ -0,0 +1,62 @@
+###################################################################
+#           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 time
+from datetime import datetime
+
+class GetTime:
+
+    def get_ms_timestamp(self,ts_str):
+        _ts_str = ts_str
+        if " " in ts_str:
+            p = ts_str.split(" ")[1]
+            if len(p) > 15 :
+                _ts_str = ts_str[:-3]
+        if ':' in _ts_str and '.' in _ts_str:
+            timestamp = datetime.strptime(_ts_str, "%Y-%m-%d %H:%M:%S.%f")
+            date_time = int(int(time.mktime(timestamp.timetuple()))*1000 + timestamp.microsecond/1000)
+        elif ':' in _ts_str and '.' not in _ts_str:
+            timestamp = datetime.strptime(_ts_str, "%Y-%m-%d %H:%M:%S")
+            date_time = int(int(time.mktime(timestamp.timetuple()))*1000 + timestamp.microsecond/1000)
+        else:
+            timestamp = datetime.strptime(_ts_str, "%Y-%m-%d")
+            date_time = int(int(time.mktime(timestamp.timetuple()))*1000 + timestamp.microsecond/1000)
+        return date_time
+    def get_us_timestamp(self,ts_str):
+        _ts = self.get_ms_timestamp(ts_str) * 1000
+        if " " in ts_str:
+            p = ts_str.split(" ")[1]
+            if len(p) > 12:
+                us_ts = p[12:15]
+                _ts += int(us_ts)
+        return _ts
+    def get_ns_timestamp(self,ts_str):
+        _ts = self.get_us_timestamp(ts_str) *1000
+        if " " in ts_str:
+            p = ts_str.split(" ")[1]
+            if len(p) > 15:
+                us_ts = p[15:]
+                _ts += int(us_ts)
+        return _ts
+    def time_transform(self,ts_str,precision):
+        date_time = []
+        if precision == 'ms':
+            for i in ts_str:
+                date_time.append(self.get_ms_timestamp(i))
+        elif precision == 'us':
+            for i in ts_str:
+                date_time.append(self.get_us_timestamp(i))
+        elif precision == 'ns':
+            for i in ts_str:
+                date_time.append(self.get_ns_timestamp(i))
+        return date_time
\ No newline at end of file
diff --git a/tests/system-test/1-insert/alter_stable.py b/tests/system-test/1-insert/alter_stable.py
index a4cec78138..b66cbb89c0 100644
--- a/tests/system-test/1-insert/alter_stable.py
+++ b/tests/system-test/1-insert/alter_stable.py
@@ -108,8 +108,8 @@ class TDTestCase:
                 tdSql.error(f'alter stable {self.stbname}_{i} add column {key} {values}')
                 tdSql.error(f'alter stable {self.stbname}_{i} drop column {key}')
             #! bug TD-16921
-            #tdSql.error(f'alter stable {self.ntbname} add column {key} {values}')
-            #tdSql.error(f'alter stable {self.ntbname} drop column {key}')
+            tdSql.error(f'alter stable {self.ntbname} add column {key} {values}')
+            tdSql.error(f'alter stable {self.ntbname} drop column {key}')
             tdSql.execute(f'alter stable {self.stbname} drop column {key}')
             tdSql.query(f'describe {self.stbname}')
             tdSql.checkRows(len(self.column_dict)+len(self.tag_dict))
@@ -132,7 +132,7 @@ class TDTestCase:
                     tdSql.checkEqual(result[0][2],self.binary_length+1)
                     tdSql.error(f'alter stable {self.stbname}_{i} modify column {key} {v}')
                #! bug TD-16921
-               # tdSql.error(f'alter stable {self.ntbname} modify column {key} {v}')
+                tdSql.error(f'alter stable {self.ntbname} modify column {key} {v}')
             elif 'nchar' in values.lower():
                 v = f'nchar({self.binary_length+1})'
                 v_error = f'nchar({self.binary_length-1})'
@@ -147,11 +147,11 @@ class TDTestCase:
                     tdSql.checkEqual(result[0][2],self.binary_length+1)
                     tdSql.error(f'alter stable {self.stbname}_{i} modify column {key} {v}')
                 #! bug TD-16921
-                #tdSql.error(f'alter stable {self.ntbname} modify column {key} {v}')
+                tdSql.error(f'alter stable {self.ntbname} modify column {key} {v}')
             else:
                 for v in self.column_dict.values():
                     tdSql.error(f'alter stable {self.stbname} modify column {key} {v}')
-                   # tdSql.error(f'alter stable {self.ntbname} modify column {key} {v}')
+                    tdSql.error(f'alter stable {self.ntbname} modify column {key} {v}')
                     for i in range(self.tbnum):
                         tdSql.error(f'alter stable {self.stbname}_{i} modify column {key} {v}')
     def run(self):
diff --git a/tests/system-test/2-query/Timediff.py b/tests/system-test/2-query/Timediff.py
index b8f3649eff..70cf34e766 100644
--- a/tests/system-test/2-query/Timediff.py
+++ b/tests/system-test/2-query/Timediff.py
@@ -1,202 +1,171 @@
 from util.log import *
 from util.sql import *
 from util.cases import *
-
+from util.gettime import *
 class TDTestCase:
 
     def init(self, conn, logSql):
         tdLog.debug(f"start to excute {__file__}")
         tdSql.init(conn.cursor())
+        self.get_time = GetTime()
+        self.ts_str = [
+            '2020-1-1',
+            '2020-2-1 00:00:01',
+            '2020-3-1 00:00:00.001',
+            '2020-4-1 00:00:00.001002',
+            '2020-5-1 00:00:00.001002001'
 
+        ]
+        self.db_param_precision = ['ms','us','ns']
+        self.time_unit = ['1w','1d','1h','1m','1s','1a','1u','1b']
+        self.error_unit = ['2w','2d','2h','2m','2s','2a','2u','1c','#1']
+        self.ntbname = 'ntb'
+        self.stbname = 'stb'
+        self.ctbname = 'ctb'
+        self.subtractor = 1  # unit:s
+    def check_tbtype(self,tb_type):
+        if tb_type.lower() == 'ntb': 
+            tdSql.query(f'select timediff(ts,{self.subtractor}) from {self.ntbname}')
+        elif tb_type.lower() == 'ctb':
+            tdSql.query(f'select timediff(ts,{self.subtractor}) from {self.ctbname}')
+        elif tb_type.lower() == 'stb':
+            tdSql.query(f'select timediff(ts,{self.subtractor}) from {self.stbname}')
+    def check_tb_type(self,unit,tb_type):
+        if tb_type.lower() == 'ntb': 
+            tdSql.query(f'select timediff(ts,{self.subtractor},{unit}) from {self.ntbname}')
+        elif tb_type.lower() == 'ctb':
+            tdSql.query(f'select timediff(ts,{self.subtractor},{unit}) from {self.ctbname}')
+        elif tb_type.lower() == 'stb':
+            tdSql.query(f'select timediff(ts,{self.subtractor},{unit}) from {self.stbname}')
+    def data_check(self,date_time,precision,tb_type):
+        for unit in self.time_unit:
+            if (unit.lower() == '1u' and precision.lower() == 'ms') or (unit.lower() == '1b' and precision.lower() == 'us') or (unit.lower() == '1b' and precision.lower() == 'ms'):
+                if tb_type.lower() == 'ntb': 
+                    tdSql.error(f'select timediff(ts,{self.subtractor},{unit}) from {self.ntbname}')
+                elif tb_type.lower() == 'ctb':
+                    tdSql.error(f'select timediff(ts,{self.subtractor},{unit}) from {self.ctbname}')
+                elif tb_type.lower() == 'stb':
+                    tdSql.error(f'select timediff(ts,{self.subtractor},{unit}) from {self.stbname}')
+            elif precision.lower() == 'ms':
+                self.check_tb_type(unit,tb_type)
+                tdSql.checkRows(len(self.ts_str))
+                if unit.lower() == '1a':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i])-self.subtractor*1000)
+                elif unit.lower() == '1s':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]/1000)-self.subtractor)
+                elif unit.lower() == '1m':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000)-self.subtractor)/60))
+                elif unit.lower() == '1h':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000)-self.subtractor)/60/60))
+                elif unit.lower() == '1d':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000)-self.subtractor)/60/60/24))        
+                elif unit.lower() == '1w':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000)-self.subtractor)/60/60/24/7))
+                self.check_tbtype(tb_type)
+                tdSql.checkRows(len(self.ts_str))
+                for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i])-self.subtractor*1000)
+            elif precision.lower() == 'us':
+                self.check_tb_type(unit,tb_type)
+                tdSql.checkRows(len(self.ts_str))
+                if unit.lower() == '1w':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000000)-self.subtractor)/60/60/24/7))
+                elif unit.lower() == '1d':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000000)-self.subtractor)/60/60/24))
+                elif unit.lower() == '1h':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000000)-self.subtractor)/60/60))
+                elif unit.lower() == '1m':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000000)-self.subtractor)/60))
+                elif unit.lower() == '1s':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000000)-self.subtractor)))
+                elif unit.lower() == '1a':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000)-self.subtractor*1000)))
+                elif unit.lower() == '1u':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i])-self.subtractor*1000000)))        
+                self.check_tbtype(tb_type)
+                tdSql.checkRows(len(self.ts_str))
+                for i in range(len(self.ts_str)):
+                    tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i])-self.subtractor*1000000)))
+            elif precision.lower() == 'ns':
+                self.check_tb_type(unit,tb_type)
+                tdSql.checkRows(len(self.ts_str))
+                if unit.lower() == '1w':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000000000)-self.subtractor)/60/60/24/7))
+                elif unit.lower() == '1d':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000000000)-self.subtractor)/60/60/24))
+                elif unit.lower() == '1h':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000000000)-self.subtractor)/60/60))
+                elif unit.lower() == '1m':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000000000)-self.subtractor)/60))
+                elif unit.lower() == '1s':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000000000)-self.subtractor)))
+                elif unit.lower() == '1a':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000000)-self.subtractor*1000)))
+                elif unit.lower() == '1u':
+                    for i in range(len(self.ts_str)):
+                        tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000)-self.subtractor*1000000)))
+                # self.check_tbtype(tb_type)
+                # tdSql.checkRows(len(self.ts_str))
+                # for i in range(len(self.ts_str)):
+                #     tdSql.checkEqual(tdSql.queryResult[i][0],int(((date_time[i]/1000000)-self.subtractor*1000000000)))
+            for unit in self.error_unit:
+                if tb_type.lower() == 'ntb':
+                    tdSql.error(f'select timediff(ts,{self.subtractor},{unit}) from {self.ntbname}')
+                    tdSql.error(f'select timediff(c0,{self.subtractor},{unit}) from {self.ntbname}')
+                elif tb_type.lower() == 'ctb':
+                    tdSql.error(f'select timediff(ts,{self.subtractor},{unit}) from {self.ctbname}')
+                    tdSql.error(f'select timediff(c0,{self.subtractor},{unit}) from {self.ntbname}')
+                elif tb_type.lower() == 'stb':
+                    tdSql.error(f'select timediff(ts,{self.subtractor},{unit}) from {self.stbname}')
+                    tdSql.error(f'select timediff(c0,{self.subtractor},{unit}) from {self.ntbname}')
+    def function_check_ntb(self):
+        for precision in self.db_param_precision:
+            tdSql.execute('drop database if exists db')
+            tdSql.execute(f'create database db precision "{precision}"')
+            tdSql.execute('use db')
+            tdSql.execute(f'create table {self.ntbname} (ts timestamp,c0 int)')
+            for ts in self.ts_str:
+                tdSql.execute(f'insert into {self.ntbname} values("{ts}",1)')
+            for unit in self.error_unit:
+                tdSql.error(f'select timediff(ts,{self.subtractor},{unit}) from {self.ntbname}')
+            date_time = self.get_time.time_transform(self.ts_str,precision)
+            self.data_check(date_time,precision,'ntb')
+    def function_check_stb(self):
+        for precision in self.db_param_precision:
+            tdSql.execute('drop database if exists db')
+            tdSql.execute(f'create database db precision "{precision}"')
+            tdSql.execute('use db')
+            tdSql.execute(f'create table {self.stbname} (ts timestamp,c0 int) tags(t0 int)')
+            tdSql.execute(f'create table {self.ctbname} using {self.stbname} tags(1)')
+            for ts in self.ts_str:
+                tdSql.execute(f'insert into {self.ctbname} values("{ts}",1)')
+            date_time = self.get_time.time_transform(self.ts_str,precision)
+            self.data_check(date_time,precision,'ctb')
+            self.data_check(date_time,precision,'stb')
     def run(self):  # sourcery skip: extract-duplicate-method
-        tdSql.prepare()
-        tdLog.printNoPrefix("==========step1:create tables==========")
-        tdSql.execute(
-            '''create table if not exists ntb
-            (ts timestamp, c1 int, c2 float,c3 double,c4 timestamp)
-            '''
-        )
-        tdSql.execute(
-            '''create table if not exists stb
-            (ts timestamp, c1 int, c2 float,c3 double,c4 timestamp) tags(t0 int)
-            '''
-        )
-        tdSql.execute(
-            '''create table if not exists stb_1 using stb tags(100)
-            '''
-        )
-        tdLog.printNoPrefix("==========step2:insert data into ntb==========")
-
-        # RFC3339:2020-01-01T00:00:00+8:00
-        # ISO8601:2020-01-01T00:00:00.000+0800
-        tdSql.execute(
-            'insert into ntb values(now,1,1.55,100.555555,today())("2020-1-1 00:00:00",10,11.11,99.999999,now())(today(),3,3.333,333.333333,now())')
-        tdSql.execute(
-            'insert into stb_1 values(now,1,1.55,100.555555,today())("2020-1-1 00:00:00",10,11.11,99.999999,now())(today(),3,3.333,333.333333,now())')
-
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00') from ntb")
-        tdSql.checkRows(3)
-        tdSql.query("select timediff(1,0,1d) from ntb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,0)
-        tdSql.query("select timediff(1,0,1d) from db.ntb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,0)
-        tdSql.query("select timediff(1,0,1s) from ntb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,1)
-        tdSql.query("select timediff(1,0,1s) from db.ntb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,1)
-        tdSql.query("select timediff(1,0,1w) from ntb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,0)
-        tdSql.query("select timediff(1,0,1w) from db.ntb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,0)
-        tdSql.query("select timediff(1,0,1h) from ntb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,0)
-        tdSql.query("select timediff(1,0,1h) from db.ntb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,0)
-        tdSql.query("select timediff(1,0,1m) from ntb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,0)
-        tdSql.query("select timediff(1,0,1m) from db.ntb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,0)
-        tdSql.query("select timediff(1,0,1a) from ntb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,1000)
-        tdSql.query("select timediff(1,0,1a) from db.ntb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,1000)
-        tdSql.error("select timediff(1,0,1u) from ntb")
-        #tdSql.checkRows(3)
-        #tdSql.checkData(0,0,1000000)
-        tdSql.error("select timediff(1,0,1u) from db.ntb")
-        #tdSql.checkRows(3)
-        #tdSql.checkData(0,0,1000000)
-
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00') from stb")
-        tdSql.checkRows(3)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00') from db.stb")
-        tdSql.checkRows(3)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00',1d) from stb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,1)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00',1d) from db.stb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,1)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00',1h) from stb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,24)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00',1h) from db.stb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,24)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00',1w) from stb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,0)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00',1m) from stb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,1440)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00',1m) from db.stb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,1440)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00',1s) from stb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,86400)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00',1s) from db.stb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,86400)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00',1a) from stb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,86400000)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00',1a) from db.stb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,86400000)
-        tdSql.error("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00',1u) from stb")
-        #tdSql.checkRows(3)
-        #tdSql.checkData(0,0,86400000000)
-        tdSql.error("select timediff('2020-1-1 00:00:00','2020-1-2 00:00:00',1u) from db.stb")
-        #tdSql.checkRows(3)
-        #tdSql.checkData(0,0,86400000000)
-
-
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00') from stb_1")
-        tdSql.checkRows(3)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00') from db.stb_1")
-        tdSql.checkRows(3)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1w) from stb_1 ")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,0)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1w) from db.stb_1 ")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,0)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1d) from stb_1 ")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,0)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1d) from db.stb_1 ")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,0)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1h) from stb_1 ")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,12)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1h) from db.stb_1 ")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,12)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1m) from stb_1" )
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,720)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1m) from db.stb_1" )
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,720)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1s) from stb_1")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,43200)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1s) from db.stb_1")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,43200)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1a) from stb_1")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,43200000)
-        tdSql.query("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1a) from db.stb_1")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,43200000)
-        tdSql.error("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1u) from stb_1")
-        #tdSql.checkRows(3)
-        #tdSql.checkData(0,0,43200000000)
-        tdSql.error("select timediff('2020-1-1 00:00:00','2020-1-1 12:00:00',1u) from db.stb_1")
-        #tdSql.checkRows(3)
-        #tdSql.checkData(0,0,43200000000)
-
-        tdSql.query("select timediff('a','b') from stb")
-        tdSql.checkRows(3)
-        tdSql.checkData(0,0,None)
-        tdSql.checkData(1,0,None)
-        tdSql.checkData(2,0,None)
-        tdSql.error("select timediff(1.5,1.5) from stb")
-        tdSql.error("select timediff(1) from stb")
-        tdSql.error("select timediff(10,1,1.5) from stb")
-        # tdSql.error("select timediff(10,1,2s) from stb")
-        # tdSql.error("select timedifff(10,1,c1) from stb")
-        tdSql.error("select timediff(1.5,1.5) from stb_1")
-        tdSql.error("select timediff(1) from stb_1")
-        tdSql.error("select timediff(10,1,1.5) from stb_1")
-        # tdSql.error("select timediff(10,1,2s) from stb_1")
-        # tdSql.error("select timedifff(10,1,c1) from stb_1")
-        tdSql.error("select timediff(1.5,1.5) from ntb")
-        tdSql.error("select timediff(1) from ntb")
-        tdSql.error("select timediff(10,1,1.5) from ntb")
-        # tdSql.error("select timediff(10,1,2s) from ntb")
-        # tdSql.error("select timedifff(10,1,c1) from ntb")
-
-
-
-
-
 
+        self.function_check_ntb()
+        self.function_check_stb()
+        
     def stop(self):
         tdSql.close()
         tdLog.success(f"{__file__} successfully executed")
diff --git a/tests/system-test/2-query/timetruncate.py b/tests/system-test/2-query/timetruncate.py
index ebc8e6b6f9..ee302a1d8e 100644
--- a/tests/system-test/2-query/timetruncate.py
+++ b/tests/system-test/2-query/timetruncate.py
@@ -5,184 +5,131 @@ from util.sql import *
 import numpy as np
 import time
 from datetime import datetime
-
+from util.gettime import *
 class TDTestCase:
     def init(self, conn, logSql):
         tdLog.debug("start to execute %s" % __file__)
         tdSql.init(conn.cursor())
-
-        self.rowNum = 10
-        self.ts = 1537146000000  # 2018-9-17 09:00:00.000
-
+        self.get_time = GetTime()
         self.ts_str = [
             '2020-1-1',
             '2020-2-1 00:00:01',
             '2020-3-1 00:00:00.001',
             '2020-4-1 00:00:00.001002',
             '2020-5-1 00:00:00.001002001'
-
         ]
         self.db_param_precision = ['ms','us','ns']
-        self.time_unit = ['1w','1d','1h','1m','1s','1a','1u']
-        #self.error_unit = ['1b','2w','2d','2h','2m','2s','2a','2u','1c','#1']
+        self.time_unit = ['1w','1d','1h','1m','1s','1a','1u','1b']
+        self.error_unit = ['2w','2d','2h','2m','2s','2a','2u','1c','#1']
         self.error_unit = ['2w','2d','2h','2m','2s','2a','2u','1c','#1']
         self.ntbname = 'ntb'
         self.stbname = 'stb'
         self.ctbname = 'ctb'
-    def get_ms_timestamp(self,ts_str):
-        _ts_str = ts_str
-        if " " in ts_str:
-            p = ts_str.split(" ")[1]
-            if len(p) > 15 :
-                _ts_str = ts_str[:-3]
-        if ':' in _ts_str and '.' in _ts_str:
-            timestamp = datetime.strptime(_ts_str, "%Y-%m-%d %H:%M:%S.%f")
-            date_time = int(int(time.mktime(timestamp.timetuple()))*1000 + timestamp.microsecond/1000)
-        elif ':' in _ts_str and '.' not in _ts_str:
-            timestamp = datetime.strptime(_ts_str, "%Y-%m-%d %H:%M:%S")
-            date_time = int(int(time.mktime(timestamp.timetuple()))*1000 + timestamp.microsecond/1000)
-        else:
-            timestamp = datetime.strptime(_ts_str, "%Y-%m-%d")
-            date_time = int(int(time.mktime(timestamp.timetuple()))*1000 + timestamp.microsecond/1000)
-        return date_time
-    def get_us_timestamp(self,ts_str):
-        _ts = self.get_ms_timestamp(ts_str) * 1000
-        if " " in ts_str:
-            p = ts_str.split(" ")[1]
-            if len(p) > 12:
-                us_ts = p[12:15]
-                _ts += int(us_ts)
-        return _ts
-    def get_ns_timestamp(self,ts_str):
-        _ts = self.get_us_timestamp(ts_str) *1000
-        if " " in ts_str:
-            p = ts_str.split(" ")[1]
-            if len(p) > 15:
-                us_ts = p[15:]
-                _ts += int(us_ts)
-        return _ts
-    def time_transform(self,ts_str,precision):
-        date_time = []
-        if precision == 'ms':
-            for i in ts_str:
-                date_time.append(self.get_ms_timestamp(i))
-        elif precision == 'us':
-            for i in ts_str:
-                date_time.append(self.get_us_timestamp(i))
-        elif precision == 'ns':
-            for i in ts_str:
-                date_time.append(self.get_us_timestamp(i))
-        return date_time
     def check_ms_timestamp(self,unit,date_time):
         if unit.lower() == '1a':
             for i in range(len(self.ts_str)):
-                ts_result = self.get_ms_timestamp(str(tdSql.queryResult[i][0]))
+                ts_result = self.get_time.get_ms_timestamp(str(tdSql.queryResult[i][0]))
                 tdSql.checkEqual(ts_result,int(date_time[i]))
         elif unit.lower() == '1s':
             for i in range(len(self.ts_str)):
-                ts_result = self.get_ms_timestamp(str(tdSql.queryResult[i][0]))
+                ts_result = self.get_time.get_ms_timestamp(str(tdSql.queryResult[i][0]))
                 tdSql.checkEqual(ts_result,int(date_time[i]/1000)*1000)
         elif unit.lower() == '1m':
             for i in range(len(self.ts_str)):
-                ts_result = self.get_ms_timestamp(str(tdSql.queryResult[i][0]))
+                ts_result = self.get_time.get_ms_timestamp(str(tdSql.queryResult[i][0]))
                 tdSql.checkEqual(ts_result,int(date_time[i]/1000/60)*60*1000)
         elif unit.lower() == '1h':
             for i in range(len(self.ts_str)):
-                ts_result = self.get_ms_timestamp(str(tdSql.queryResult[i][0]))
+                ts_result = self.get_time.get_ms_timestamp(str(tdSql.queryResult[i][0]))
                 tdSql.checkEqual(ts_result,int(date_time[i]/1000/60/60)*60*60*1000  )
         elif unit.lower() == '1d':
             for i in range(len(self.ts_str)):
-                ts_result = self.get_ms_timestamp(str(tdSql.queryResult[i][0]))
-                tdSql.checkEqual(ts_result,int(date_time[i]/1000/60/60/24)*24*60*60*1000)
+                ts_result = self.get_time.get_ms_timestamp(str(tdSql.queryResult[i][0]))
+                tdSql.checkEqual(ts_result,int(date_time[i]/1000/60/60/24)*24*60*60*1000)  
         elif unit.lower() == '1w':
             for i in range(len(self.ts_str)):
-                ts_result = self.get_ms_timestamp(str(tdSql.queryResult[i][0]))
+                ts_result = self.get_time.get_ms_timestamp(str(tdSql.queryResult[i][0]))
                 tdSql.checkEqual(ts_result,int(date_time[i]/1000/60/60/24/7)*7*24*60*60*1000)
     def check_us_timestamp(self,unit,date_time):
         if unit.lower() == '1u':
             for i in range(len(self.ts_str)):
-                ts_result = self.get_us_timestamp(str(tdSql.queryResult[i][0]))
+                ts_result = self.get_time.get_us_timestamp(str(tdSql.queryResult[i][0]))
                 tdSql.checkEqual(ts_result,int(date_time[i]))
         elif unit.lower() == '1a':
             for i in range(len(self.ts_str)):
-                ts_result = self.get_us_timestamp(str(tdSql.queryResult[i][0]))
+                ts_result = self.get_time.get_us_timestamp(str(tdSql.queryResult[i][0]))
                 tdSql.checkEqual(ts_result,int(date_time[i]/1000)*1000)
         elif unit.lower() == '1s':
             for i in range(len(self.ts_str)):
-                ts_result = self.get_us_timestamp(str(tdSql.queryResult[i][0]))
+                ts_result = self.get_time.get_us_timestamp(str(tdSql.queryResult[i][0]))
                 tdSql.checkEqual(ts_result,int(date_time[i]/1000/1000)*1000*1000)
         elif unit.lower() == '1m':
             for i in range(len(self.ts_str)):
-                ts_result = self.get_us_timestamp(str(tdSql.queryResult[i][0]))
+                ts_result = self.get_time.get_us_timestamp(str(tdSql.queryResult[i][0]))
                 tdSql.checkEqual(ts_result,int(date_time[i]/1000/1000/60)*60*1000*1000)
         elif unit.lower() == '1h':
             for i in range(len(self.ts_str)):
-                ts_result = self.get_us_timestamp(str(tdSql.queryResult[i][0]))
+                ts_result = self.get_time.get_us_timestamp(str(tdSql.queryResult[i][0]))
                 tdSql.checkEqual(ts_result,int(date_time[i]/1000/1000/60/60)*60*60*1000*1000  )
         elif unit.lower() == '1d':
             for i in range(len(self.ts_str)):
-                ts_result = self.get_us_timestamp(str(tdSql.queryResult[i][0]))
-                tdSql.checkEqual(ts_result,int(date_time[i]/1000/1000/60/60/24)*24*60*60*1000*1000 )
+                ts_result = self.get_time.get_us_timestamp(str(tdSql.queryResult[i][0]))
+                tdSql.checkEqual(ts_result,int(date_time[i]/1000/1000/60/60/24)*24*60*60*1000*1000 ) 
         elif unit.lower() == '1w':
             for i in range(len(self.ts_str)):
-                ts_result = self.get_us_timestamp(str(tdSql.queryResult[i][0]))
+                ts_result = self.get_time.get_us_timestamp(str(tdSql.queryResult[i][0]))
                 tdSql.checkEqual(ts_result,int(date_time[i]/1000/1000/60/60/24/7)*7*24*60*60*1000*1000)
     def check_ns_timestamp(self,unit,date_time):
-        if unit.lower() == '1u':
+        if unit.lower() == '1b':
             for i in range(len(self.ts_str)):
-                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000)*1000)
+                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]))
+        elif unit.lower() == '1u':
+            for i in range(len(self.ts_str)):
+                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000/1000)*1000)
         elif unit.lower() == '1a':
             for i in range(len(self.ts_str)):
-                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000/1000)*1000*1000)
+                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000/1000/1000)*1000*1000)
         elif unit.lower() == '1s':
             for i in range(len(self.ts_str)):
-                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000/1000/1000)*1000*1000*1000)
+                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000/1000/1000/1000)*1000*1000*1000)
         elif unit.lower() == '1m':
             for i in range(len(self.ts_str)):
-                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000/1000/1000/60)*60*1000*1000*1000)
+                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000/1000/1000/1000/60)*60*1000*1000*1000)
         elif unit.lower() == '1h':
             for i in range(len(self.ts_str)):
-                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000/1000/1000/60/60)*60*60*1000*1000*1000  )
+                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000/1000/1000/1000/60/60)*60*60*1000*1000*1000  )
         elif unit.lower() == '1d':
             for i in range(len(self.ts_str)):
-                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000/1000/1000/60/60/24)*24*60*60*1000*1000*1000 )
+                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000/1000/1000/1000/60/60/24)*24*60*60*1000*1000*1000 ) 
         elif unit.lower() == '1w':
             for i in range(len(self.ts_str)):
-                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000/1000/1000/60/60/24/7)*7*24*60*60*1000*1000*1000)
+                tdSql.checkEqual(tdSql.queryResult[i][0],int(date_time[i]*1000/1000/1000/1000/1000/60/60/24/7)*7*24*60*60*1000*1000*1000)
+    def check_tb_type(self,unit,tb_type):
+        if tb_type.lower() == 'ntb': 
+            tdSql.query(f'select timetruncate(ts,{unit}) from {self.ntbname}')
+        elif tb_type.lower() == 'ctb':
+            tdSql.query(f'select timetruncate(ts,{unit}) from {self.ctbname}')
+        elif tb_type.lower() == 'stb':
+            tdSql.query(f'select timetruncate(ts,{unit}) from {self.stbname}')
     def data_check(self,date_time,precision,tb_type):
         for unit in self.time_unit:
-            if (unit.lower() == '1u' and precision.lower() == 'ms') or () :
-                if tb_type.lower() == 'ntb':
+            if (unit.lower() == '1u' and precision.lower() == 'ms') or (unit.lower() == '1b' and precision.lower() == 'us') or (unit.lower() == '1b' and precision.lower() == 'ms'):
+                if tb_type.lower() == 'ntb': 
                     tdSql.error(f'select timetruncate(ts,{unit}) from {self.ntbname}')
                 elif tb_type.lower() == 'ctb':
                     tdSql.error(f'select timetruncate(ts,{unit}) from {self.ctbname}')
                 elif tb_type.lower() == 'stb':
                     tdSql.error(f'select timetruncate(ts,{unit}) from {self.stbname}')
             elif precision.lower() == 'ms':
-                if tb_type.lower() == 'ntb':
-                    tdSql.query(f'select timetruncate(ts,{unit}) from {self.ntbname}')
-                elif tb_type.lower() == 'ctb':
-                    tdSql.query(f'select timetruncate(ts,{unit}) from {self.ctbname}')
-                elif tb_type.lower() == 'stb':
-                    tdSql.query(f'select timetruncate(ts,{unit}) from {self.stbname}')
+                self.check_tb_type(unit,tb_type)
                 tdSql.checkRows(len(self.ts_str))
                 self.check_ms_timestamp(unit,date_time)
             elif precision.lower() == 'us':
-                if tb_type.lower() == 'ntb':
-                    tdSql.query(f'select timetruncate(ts,{unit}) from {self.ntbname}')
-                elif tb_type.lower() == 'ctb':
-                    tdSql.query(f'select timetruncate(ts,{unit}) from {self.ctbname}')
-                elif tb_type.lower() == 'stb':
-                    tdSql.query(f'select timetruncate(ts,{unit}) from {self.stbname}')
+                self.check_tb_type(unit,tb_type)
                 tdSql.checkRows(len(self.ts_str))
                 self.check_us_timestamp(unit,date_time)
             elif precision.lower() == 'ns':
-                if tb_type.lower() == 'ntb':
-                    tdSql.query(f'select timetruncate(ts,{unit}) from {self.ntbname}')
-                elif tb_type.lower() == 'ctb':
-                    tdSql.query(f'select timetruncate(ts,{unit}) from {self.ctbname}')
-                elif tb_type.lower() == 'stb':
-                    tdSql.query(f'select timetruncate(ts,{unit}) from {self.stbname}')
+                self.check_tb_type(unit,tb_type)
                 tdSql.checkRows(len(self.ts_str))
                 self.check_ns_timestamp(unit,date_time)
         for unit in self.error_unit:
@@ -200,9 +147,8 @@ class TDTestCase:
             tdSql.execute(f'create table {self.ntbname} (ts timestamp,c0 int)')
             for ts in self.ts_str:
                 tdSql.execute(f'insert into {self.ntbname} values("{ts}",1)')
-            date_time = self.time_transform(self.ts_str,precision)
+            date_time = self.get_time.time_transform(self.ts_str,precision)
             self.data_check(date_time,precision,'ntb')
-
     def function_check_stb(self):
         for precision in self.db_param_precision:
             tdSql.execute('drop database if exists db')
@@ -212,7 +158,7 @@ class TDTestCase:
             tdSql.execute(f'create table {self.ctbname} using {self.stbname} tags(1)')
             for ts in self.ts_str:
                 tdSql.execute(f'insert into {self.ctbname} values("{ts}",1)')
-            date_time = self.time_transform(self.ts_str,precision)
+            date_time = self.get_time.time_transform(self.ts_str,precision)
             self.data_check(date_time,precision,'ctb')
             self.data_check(date_time,precision,'stb')
     def run(self):