diff --git a/include/common/tdatablock.h b/include/common/tdatablock.h
index a4f59040184221db85ac41a68e3e62f9e21398e9..22aac465606a2068d2813bf6349334b322542849 100644
--- a/include/common/tdatablock.h
+++ b/include/common/tdatablock.h
@@ -184,8 +184,8 @@ static FORCE_INLINE void colDataAppendDouble(SColumnInfoData* pColumnInfoData, u
 int32_t getJsonValueLen(const char* data);
 
 int32_t colDataAppend(SColumnInfoData* pColumnInfoData, uint32_t currentRow, const char* pData, bool isNull);
-int32_t colDataMergeCol(SColumnInfoData* pColumnInfoData, uint32_t numOfRow1, uint32_t* capacity,
-                        const SColumnInfoData* pSource, uint32_t numOfRow2);
+int32_t colDataMergeCol(SColumnInfoData* pColumnInfoData, int32_t numOfRow1, int32_t* capacity,
+                        const SColumnInfoData* pSource, int32_t numOfRow2);
 int32_t colDataAssign(SColumnInfoData* pColumnInfoData, const SColumnInfoData* pSource, int32_t numOfRows,
                       const SDataBlockInfo* pBlockInfo);
 int32_t blockDataUpdateTsWindow(SSDataBlock* pDataBlock, int32_t tsColumnIndex);
diff --git a/source/common/src/tdatablock.c b/source/common/src/tdatablock.c
index f7b0da0014ee3d0bf0938817e4ea752a73ed4296..a5b34d89a0b5d3c0aede59a1f4621440576478ac 100644
--- a/source/common/src/tdatablock.c
+++ b/source/common/src/tdatablock.c
@@ -214,8 +214,8 @@ static void doBitmapMerge(SColumnInfoData* pColumnInfoData, int32_t numOfRow1, c
   }
 }
 
-int32_t colDataMergeCol(SColumnInfoData* pColumnInfoData, uint32_t numOfRow1, uint32_t* capacity,
-                        const SColumnInfoData* pSource, uint32_t numOfRow2) {
+int32_t colDataMergeCol(SColumnInfoData* pColumnInfoData, int32_t numOfRow1, int32_t* capacity,
+                        const SColumnInfoData* pSource, int32_t numOfRow2) {
   ASSERT(pColumnInfoData != NULL && pSource != NULL && pColumnInfoData->info.type == pSource->info.type);
   if (numOfRow2 == 0) {
     return numOfRow1;
@@ -369,6 +369,10 @@ int32_t blockDataMerge(SSDataBlock* pDest, const SSDataBlock* pSrc) {
     SColumnInfoData* pCol2 = taosArrayGet(pDest->pDataBlock, i);
     SColumnInfoData* pCol1 = taosArrayGet(pSrc->pDataBlock, i);
 
+    if (pCol1->info.type == 0) {  // ignore null type
+      continue;
+    }
+
     capacity = pDest->info.capacity;
     colDataMergeCol(pCol2, pDest->info.rows, &capacity, pCol1, pSrc->info.rows);
   }