diff --git a/src/client/src/tscFunctionImpl.c b/src/client/src/tscFunctionImpl.c
index d8ac0d3109fc207278882e365724879a8114897a..be38a7af71ed8b97f9deb001b7bbc4fef80104e6 100644
--- a/src/client/src/tscFunctionImpl.c
+++ b/src/client/src/tscFunctionImpl.c
@@ -326,7 +326,7 @@ int32_t getResultDataInfo(int32_t dataType, int32_t dataBytes, int32_t functionI
   } else if (functionId == TSDB_FUNC_LAST_ROW) {
     *type = (int16_t)dataType;
     *bytes = (int16_t)dataBytes;
-    *interBytes = dataBytes + sizeof(SLastrowInfo);
+    *interBytes = dataBytes;
   } else {
     return TSDB_CODE_TSC_INVALID_SQL;
   }
@@ -1843,8 +1843,10 @@ static void last_row_function(SQLFunctionCtx *pCtx) {
     pInfo1->hasResult = DATA_SET_FLAG;
     
     DO_UPDATE_TAG_COLUMNS(pCtx, pInfo1->ts);
+  } else {
+    DO_UPDATE_TAG_COLUMNS(pCtx, pCtx->ptsList[pCtx->size - 1]);
   }
-  
+
   SET_VAL(pCtx, pCtx->size, 1);
 }
 
diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index cceb876a06d65dcc07af5e8157aa27548fdc8f01..4555b0e08d362e528cde070e2f7ff1a2b0020e20 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -5286,9 +5286,12 @@ void doAddGroupColumnForSubquery(SQueryInfo* pQueryInfo, int32_t tagIndex) {
 
 static void doUpdateSqlFunctionForTagPrj(SQueryInfo* pQueryInfo) {
   int32_t tagLength = 0;
-  
   size_t size = taosArrayGetSize(pQueryInfo->exprList);
-  
+
+//todo is 0??
+  STableMetaInfo* pTableMetaInfo = tscGetMetaInfo(pQueryInfo, 0);
+  bool isSTable = UTIL_TABLE_IS_SUPER_TABLE(pTableMetaInfo);
+
   for (int32_t i = 0; i < size; ++i) {
     SSqlExpr* pExpr = tscSqlExprGet(pQueryInfo, i);
     if (pExpr->functionId == TSDB_FUNC_TAGPRJ || pExpr->functionId == TSDB_FUNC_TAG) {
@@ -5300,8 +5303,7 @@ static void doUpdateSqlFunctionForTagPrj(SQueryInfo* pQueryInfo) {
     }
   }
 
-  STableMetaInfo* pTableMetaInfo = tscGetMetaInfo(pQueryInfo, 0);
-  SSchema*        pSchema = tscGetTableSchema(pTableMetaInfo->pTableMeta);
+  SSchema* pSchema = tscGetTableSchema(pTableMetaInfo->pTableMeta);
 
   for (int32_t i = 0; i < size; ++i) {
     SSqlExpr* pExpr = tscSqlExprGet(pQueryInfo, i);
@@ -5309,7 +5311,7 @@ static void doUpdateSqlFunctionForTagPrj(SQueryInfo* pQueryInfo) {
        !(pExpr->functionId == TSDB_FUNC_PRJ && TSDB_COL_IS_UD_COL(pExpr->colInfo.flag))) {
       SSchema* pColSchema = &pSchema[pExpr->colInfo.colIndex];
       getResultDataInfo(pColSchema->type, pColSchema->bytes, pExpr->functionId, (int32_t)pExpr->param[0].i64Key, &pExpr->resType,
-                        &pExpr->resBytes, &pExpr->interBytes, tagLength, true);
+                        &pExpr->resBytes, &pExpr->interBytes, tagLength, isSTable);
     }
   }
 }
@@ -5320,7 +5322,7 @@ static int32_t doUpdateSqlFunctionForColPrj(SQueryInfo* pQueryInfo) {
   for (int32_t i = 0; i < size; ++i) {
     SSqlExpr* pExpr = tscSqlExprGet(pQueryInfo, i);
 
-    if (pExpr->functionId == TSDB_FUNC_PRJ && (!TSDB_COL_IS_UD_COL(pExpr->colInfo.flag))) {
+    if (pExpr->functionId == TSDB_FUNC_PRJ && (!TSDB_COL_IS_UD_COL(pExpr->colInfo.flag) && (pExpr->colInfo.colId != PRIMARYKEY_TIMESTAMP_COL_INDEX))) {
       bool qualifiedCol = false;
       for (int32_t j = 0; j < pQueryInfo->groupbyExpr.numOfGroupCols; ++j) {
         SColIndex* pColIndex = taosArrayGet(pQueryInfo->groupbyExpr.columnInfo, j);
@@ -5418,13 +5420,6 @@ static int32_t checkUpdateTagPrjFunctions(SQueryInfo* pQueryInfo, SSqlCmd* pCmd)
   int16_t numOfSelectivity = 0;
   int16_t numOfAggregation = 0;
 
-  // todo is 0??
-  STableMetaInfo* pTableMetaInfo = tscGetMetaInfo(pQueryInfo, 0);
-  bool isSTable = UTIL_TABLE_IS_SUPER_TABLE(pTableMetaInfo);
-  if (!isSTable) {
-    return TSDB_CODE_SUCCESS;
-  }
-
   size_t numOfExprs = taosArrayGetSize(pQueryInfo->exprList);
   for (int32_t i = 0; i < numOfExprs; ++i) {
     SSqlExpr* pExpr = taosArrayGetP(pQueryInfo->exprList, i);
diff --git a/src/query/src/qExecutor.c b/src/query/src/qExecutor.c
index d3f44cdcc715bb236fafaa4947a54771052df307..f2d324e376390e27252c22af0d8c07b5e587b20a 100644
--- a/src/query/src/qExecutor.c
+++ b/src/query/src/qExecutor.c
@@ -2120,7 +2120,7 @@ static bool needToLoadDataBlock(SQueryRuntimeEnv* pRuntimeEnv, SDataStatis *pDat
       }
     }
 
-    // no statistics data
+    // no statistics data, load the true data block
     if (index == -1) {
       return true;
     }
@@ -2130,8 +2130,17 @@ static bool needToLoadDataBlock(SQueryRuntimeEnv* pRuntimeEnv, SDataStatis *pDat
       return true;
     }
 
-    // all points in current column are NULL, no need to check its boundary value
+    // all data in current column are NULL, no need to check its boundary value
     if (pDataStatis[index].numOfNull == numOfRows) {
+
+      // if isNULL query exists, load the null data column
+      for (int32_t j = 0; j < pFilterInfo->numOfFilters; ++j) {
+        SColumnFilterElem *pFilterElem = &pFilterInfo->pFilters[j];
+        if (pFilterElem->fp == isNull_filter) {
+          return true;
+        }
+      }
+
       continue;
     }
 
@@ -2957,11 +2966,10 @@ int32_t mergeIntoGroupResultImpl(SQInfo *pQInfo, SArray *pGroup) {
     STableQueryInfo *item = taosArrayGetP(pGroup, i);
 
     SIDList list = getDataBufPagesIdList(pRuntimeEnv->pResultBuf, TSDB_TABLEID(item->pTable)->tid);
-    pageList = list;
-    tid = TSDB_TABLEID(item->pTable)->tid;
-
     if (taosArrayGetSize(list) > 0 && item->windowResInfo.size > 0) {
       pTableList[numOfTables++] = item;
+      tid = TSDB_TABLEID(item->pTable)->tid;
+      pageList = list;
     }
   }
 
diff --git a/tests/script/general/parser/where.sim b/tests/script/general/parser/where.sim
index fb15fb6dbe0f641d9d94c284d29b3ae7fbcb0f94..f9fd919bd6c5a424ddcac52a0d00b142168702e9 100644
--- a/tests/script/general/parser/where.sim
+++ b/tests/script/general/parser/where.sim
@@ -308,13 +308,25 @@ sleep 2000
 
 system sh/exec.sh -n dnode1 -s start
 
-sql select * from wh_mt0 where c3 = 'abc' and tbname in ('test_null_filter');
+sql_error select * from wh_mt0 where c3 = 'abc' and tbname in ('test_null_filter');
+
+sql select * from wh_mt0 where c3 = '1' and tbname in ('test_null_filter');
 if $row != 0 then
   return -1
 endi
 
-sql select * from wh_mt0 where c3 = 'abc' and tbname in ('test_null_filter');
-if $row != 0 then
+sql select * from wh_mt0 where c3 = '1';
+if $row == 0 then
+  return -1
+endi
+
+sql select * from wh_mt0 where c3 is null and tbname in ('test_null_filter');
+if $rows != 10000 then
+  return -1
+endi
+
+sql select * from wh_mt0 where c3 is not null and tbname in ('test_null_filter');
+if $rows != 0 then
   return -1
 endi