diff --git a/source/libs/scalar/src/filter.c b/source/libs/scalar/src/filter.c
index ca03d125b6..4befe29e1d 100644
--- a/source/libs/scalar/src/filter.c
+++ b/source/libs/scalar/src/filter.c
@@ -336,6 +336,10 @@ int8_t filterGetCompFuncIdx(int32_t type, int32_t optr) {
 __compar_fn_t filterGetCompFunc(int32_t type, int32_t optr) { return gDataCompare[filterGetCompFuncIdx(type, optr)]; }
 
 __compar_fn_t filterGetCompFuncEx(int32_t lType, int32_t rType, int32_t optr) {
+  if (TSDB_DATA_TYPE_NULL == rType) {
+    return NULL;
+  }
+  
   switch (lType) {
     case TSDB_DATA_TYPE_TINYINT: {
       if (IS_SIGNED_NUMERIC_TYPE(rType) || IS_FLOAT_TYPE(rType)) {
diff --git a/source/libs/scalar/src/scalar.c b/source/libs/scalar/src/scalar.c
index 00d6ea21a4..44f792869e 100644
--- a/source/libs/scalar/src/scalar.c
+++ b/source/libs/scalar/src/scalar.c
@@ -603,8 +603,9 @@ int32_t sclWalkCaseWhenList(SScalarCtx *ctx, SNodeList *pList, struct SListCell
 
     bool *equal = (bool *)colDataGetData(pComp->columnData, rowIdx);
     if (*equal) {
-      colDataAppend(output->columnData, rowIdx, colDataGetData(pThen->columnData, (pThen->numOfRows > 1 ? rowIdx : 0)),
-                    colDataIsNull_s(pThen->columnData, (pThen->numOfRows > 1 ? rowIdx : 0)));
+      bool isNull = colDataIsNull_s(pThen->columnData, (pThen->numOfRows > 1 ? rowIdx : 0));
+      char *pData = isNull ? NULL : colDataGetData(pThen->columnData, (pThen->numOfRows > 1 ? rowIdx : 0));
+      colDataAppend(output->columnData, rowIdx, pData, isNull);
 
       if (0 == rowIdx && 1 == pCase->numOfRows && 1 == pWhen->numOfRows && 1 == pThen->numOfRows && totalRows > 1) {
         SCL_ERR_JRET(sclExtendResRows(output, output, ctx->pBlockList));
@@ -616,8 +617,9 @@ int32_t sclWalkCaseWhenList(SScalarCtx *ctx, SNodeList *pList, struct SListCell
   }
 
   if (pElse) {
-    colDataAppend(output->columnData, rowIdx, colDataGetData(pElse->columnData, (pElse->numOfRows > 1 ? rowIdx : 0)),
-                  colDataIsNull_s(pElse->columnData, (pElse->numOfRows > 1 ? rowIdx : 0)));
+    bool isNull = colDataIsNull_s(pElse->columnData, (pElse->numOfRows > 1 ? rowIdx : 0));
+    char *pData = isNull ? NULL : colDataGetData(pElse->columnData, (pElse->numOfRows > 1 ? rowIdx : 0));
+    colDataAppend(output->columnData, rowIdx, pData, isNull);
 
     if (0 == rowIdx && 1 == pCase->numOfRows && 1 == pElse->numOfRows && totalRows > 1) {
       SCL_ERR_JRET(sclExtendResRows(output, output, ctx->pBlockList));
@@ -664,8 +666,9 @@ int32_t sclWalkWhenList(SScalarCtx *ctx, SNodeList *pList, struct SListCell *pCe
     bool *whenValue = (bool *)colDataGetData(pWhen->columnData, (pWhen->numOfRows > 1 ? rowIdx : 0));
 
     if (*whenValue) {
-      colDataAppend(output->columnData, rowIdx, colDataGetData(pThen->columnData, (pThen->numOfRows > 1 ? rowIdx : 0)),
-                    colDataIsNull_s(pThen->columnData, (pThen->numOfRows > 1 ? rowIdx : 0)));
+      bool isNull = colDataIsNull_s(pThen->columnData, (pThen->numOfRows > 1 ? rowIdx : 0));
+      char *pData = isNull ? NULL : colDataGetData(pThen->columnData, (pThen->numOfRows > 1 ? rowIdx : 0));
+      colDataAppend(output->columnData, rowIdx, pData, isNull);
 
       if (preSingle && 0 == rowIdx && 1 == pWhen->numOfRows && 1 == pThen->numOfRows && totalRows > 1) {
         SCL_ERR_JRET(sclExtendResRows(output, output, ctx->pBlockList));
@@ -682,8 +685,9 @@ int32_t sclWalkWhenList(SScalarCtx *ctx, SNodeList *pList, struct SListCell *pCe
   }
 
   if (pElse) {
-    colDataAppend(output->columnData, rowIdx, colDataGetData(pElse->columnData, (pElse->numOfRows > 1 ? rowIdx : 0)),
-                  colDataIsNull_s(pElse->columnData, (pElse->numOfRows > 1 ? rowIdx : 0)));
+    bool isNull = colDataIsNull_s(pElse->columnData, (pElse->numOfRows > 1 ? rowIdx : 0));
+    char *pData = isNull ? NULL : colDataGetData(pElse->columnData, (pElse->numOfRows > 1 ? rowIdx : 0));
+    colDataAppend(output->columnData, rowIdx, pData, isNull);
 
     if (preSingle && 0 == rowIdx && 1 == pElse->numOfRows && totalRows > 1) {
       SCL_ERR_JRET(sclExtendResRows(output, output, ctx->pBlockList));