diff --git a/source/dnode/vnode/src/tsdb/tsdbRead.c b/source/dnode/vnode/src/tsdb/tsdbRead.c
index b9ef72edc5..f0aa4d2ac6 100644
--- a/source/dnode/vnode/src/tsdb/tsdbRead.c
+++ b/source/dnode/vnode/src/tsdb/tsdbRead.c
@@ -2077,10 +2077,10 @@ static void doMergeTwoLevelData(STsdbReadHandle* pTsdbReadHandle, STableCheckInf
 #endif
         if (TD_SUPPORT_UPDATE(pCfg->update)) {
           if (lastKeyAppend != key) {
-            lastKeyAppend = key;
             if (lastKeyAppend != TSKEY_INITIAL_VAL) {
               ++curRow;
             }
+            lastKeyAppend = key;
           }
           // load data from file firstly
           numOfRows = doCopyRowsFromFileBlock(pTsdbReadHandle, pTsdbReadHandle->outputCapacity, curRow, pos, pos);
diff --git a/tests/script/tsim/insert/update0.sim b/tests/script/tsim/insert/update0.sim
index c34a08c79d..89eecaf860 100644
--- a/tests/script/tsim/insert/update0.sim
+++ b/tests/script/tsim/insert/update0.sim
@@ -35,7 +35,7 @@ sql insert into ct1 values('2022-05-03 16:59:00.016', 18);
 sql insert into ct1 values('2022-05-03 16:59:00.021', 21);
 sql insert into ct1 values('2022-05-03 16:59:00.022', 22);
 
-print =============== step3-1 query records from ct1 from memory
+print =============== step3-1 query records of ct1 from memory
 sql select * from ct1;
 print $data00 $data01
 print $data10 $data11
@@ -69,7 +69,7 @@ sql insert into ct2 values('2022-03-02 16:59:00.010', 1),('2022-03-02 16:59:00.0
 sql insert into ct2 values('2022-03-02 16:59:00.010', 3),('2022-03-02 16:59:00.010',33),('2022-04-01 16:59:00.011',4),('2022-04-01 16:59:00.011',6),('2022-03-06 16:59:00.013',8);
 sql insert into ct2 values('2022-03-02 16:59:00.010', 103),('2022-03-02 16:59:00.010',303),('2022-04-01 16:59:00.011',40),('2022-04-01 16:59:00.011',60),('2022-03-06 16:59:00.013',80);
 
-print =============== step3-1 query records from ct2 from memory
+print =============== step3-1 query records of ct2 from memory
 sql select * from ct2;
 print $data00 $data01
 print $data10 $data11
@@ -99,7 +99,7 @@ endi
 system sh/exec.sh -n dnode1 -s stop -x SIGINT
 system sh/exec.sh -n dnode1 -s start
 
-print =============== step3-2 query records from ct1 from file
+print =============== step3-2 query records of ct1 from file
 sql select * from ct1;
 print $data00 $data01
 print $data10 $data11
@@ -128,7 +128,7 @@ if $data51 != 22 then
   return -1
 endi
 
-print =============== step3-2 query records from ct2 from file
+print =============== step3-2 query records of ct2 from file
 sql select * from ct2;
 print $data00 $data01
 print $data10 $data11
@@ -152,4 +152,79 @@ endi
 if $data21 != 40 then
   print data21 $data21 != 40
   return -1
+endi
+
+print =============== step3-3 query records of ct1 from memory and file(merge)
+sql insert into ct1 values('2022-05-03 16:59:00.010', 100);
+sql insert into ct1 values('2022-05-03 16:59:00.022', 200);
+sql insert into ct1 values('2022-05-03 16:59:00.016', 160);
+
+sql select * from ct1;
+print $data00 $data01
+print $data10 $data11
+print $data20 $data21
+print $data30 $data31
+print $data40 $data41
+print $data50 $data51
+
+if $rows != 6 then 
+  print rows $rows != 6
+  return -1
+endi
+
+if $data01 != 100 then
+  print data01 $data01 != 100
+  return -1
+endi
+
+if $data21 != 160 then
+  print data21 $data21 != 160
+  return -1
+endi
+
+if $data51 != 200 then
+  print data51 $data51 != 200
+  return -1
+endi
+
+print =============== step3-3 query records of ct2 from memory and file(merge)
+sql insert into ct2(ts) values('2022-04-02 16:59:00.016');
+sql insert into ct2 values('2022-03-06 16:59:00.013', NULL);
+sql insert into ct2 values('2022-03-01 16:59:00.016', 10);
+sql insert into ct2(ts) values('2022-04-01 16:59:00.011');
+sql select * from ct2;
+print $data00 $data01
+print $data10 $data11
+print $data20 $data21
+print $data30 $data31
+print $data40 $data41
+
+if $rows != 5 then 
+  print rows $rows != 5
+  return -1
+endi
+
+if $data01 != 10 then
+  print data01 $data01 != 10
+  return -1
+endi
+
+if $data11 != 103 then
+  print data11 $data11 != 103
+  return -1
+endi
+
+if $data21 != NULL then
+  print data21 $data21 != NULL
+  return -1
+endi
+
+if $data31 != 40 then
+  print data31 $data31 != 40
+  return -1
+endi
+
+if $data41 != NULL then
+  print data41 $data41 != NULL
+  return -1
 endi
\ No newline at end of file