diff --git a/src/client/inc/tsclient.h b/src/client/inc/tsclient.h
index 47f8732de9475c4eeb78d8f805d5362b40db9278..aecbdd82075e747d613171569c62ef83e0219f1d 100644
--- a/src/client/inc/tsclient.h
+++ b/src/client/inc/tsclient.h
@@ -433,31 +433,36 @@ static FORCE_INLINE void tscGetResultColumnChr(SSqlRes* pRes, SFieldInfo* pField
   int32_t bytes = pInfo->pSqlExpr->resBytes;
 
   char* pData = pRes->data + pInfo->pSqlExpr->offset * pRes->numOfRows + bytes * pRes->row;
-  if (type == TSDB_DATA_TYPE_NCHAR || type == TSDB_DATA_TYPE_BINARY) {
-    int32_t realLen = varDataLen(pData);
-    assert(realLen <= bytes - VARSTR_HEADER_SIZE);
 
-    if (isNull(pData, type)) {
-      pRes->tsrow[columnIndex] = NULL;
+  // user defined constant value output columns
+  if (pInfo->pSqlExpr->colInfo.flag == TSDB_COL_UDC) {
+    if (type == TSDB_DATA_TYPE_NCHAR || type == TSDB_DATA_TYPE_BINARY) {
+      pData = pInfo->pSqlExpr->param[1].pz;
+      pRes->length[columnIndex] = pInfo->pSqlExpr->param[1].nLen;
+      pRes->tsrow[columnIndex] = (pInfo->pSqlExpr->param[1].nType == TSDB_DATA_TYPE_NULL) ? NULL : pData;
     } else {
-      pRes->tsrow[columnIndex] = ((tstr*)pData)->data;
-    }
+      assert(bytes == tDataTypeDesc[type].nSize);
 
-    if (realLen < pInfo->pSqlExpr->resBytes - VARSTR_HEADER_SIZE) { // todo refactor
-      *(pData + realLen + VARSTR_HEADER_SIZE) = 0;
+      pRes->tsrow[columnIndex] = isNull(pData, type) ? NULL : &pInfo->pSqlExpr->param[1].i64Key;
+      pRes->length[columnIndex] = bytes;
     }
-
-    pRes->length[columnIndex] = realLen;
   } else {
-    assert(bytes == tDataTypeDesc[type].nSize);
+    if (type == TSDB_DATA_TYPE_NCHAR || type == TSDB_DATA_TYPE_BINARY) {
+      int32_t realLen = varDataLen(pData);
+      assert(realLen <= bytes - VARSTR_HEADER_SIZE);
+
+      pRes->tsrow[columnIndex] = (isNull(pData, type)) ? NULL : ((tstr *)pData)->data;
+      if (realLen < pInfo->pSqlExpr->resBytes - VARSTR_HEADER_SIZE) {  // todo refactor
+        *(pData + realLen + VARSTR_HEADER_SIZE) = 0;
+      }
 
-    if (isNull(pData, type)) {
-      pRes->tsrow[columnIndex] = NULL;
+      pRes->length[columnIndex] = realLen;
     } else {
-      pRes->tsrow[columnIndex] = pData;
-    }
+      assert(bytes == tDataTypeDesc[type].nSize);
 
-    pRes->length[columnIndex] = bytes;
+      pRes->tsrow[columnIndex] = isNull(pData, type) ? NULL : pData;
+      pRes->length[columnIndex] = bytes;
+    }
   }
 }
 
diff --git a/src/client/src/tscFunctionImpl.c b/src/client/src/tscFunctionImpl.c
index b5c17e57b90ce8e3bf788585ed68599e28deb13e..a0ef40d36708bde030825504ec6b29970337fdc4 100644
--- a/src/client/src/tscFunctionImpl.c
+++ b/src/client/src/tscFunctionImpl.c
@@ -2902,27 +2902,20 @@ static FORCE_INLINE void date_col_output_function_f(SQLFunctionCtx *pCtx, int32_
 }
 
 static void col_project_function(SQLFunctionCtx *pCtx) {
-  if (pCtx->numOfParams == 2) {  // the number of output rows should not affect the final number of rows, so set it to be 0
-    SET_VAL(pCtx, pCtx->size, 1);
+  // the number of output rows should not affect the final number of rows, so set it to be 0
+  if (pCtx->numOfParams == 2) {
+    return;
+  }
 
-    char* output = pCtx->aOutputBuf;
-    for(int32_t i = 0; i < pCtx->size; ++i) {
-      tVariantDump(&pCtx->param[1], output, pCtx->outputType, true);
-      output += pCtx->outputBytes;
-    }
+  INC_INIT_VAL(pCtx, pCtx->size);
 
+  char *pData = GET_INPUT_CHAR(pCtx);
+  if (pCtx->order == TSDB_ORDER_ASC) {
+    memcpy(pCtx->aOutputBuf, pData, (size_t) pCtx->size * pCtx->inputBytes);
   } else {
-
-    INC_INIT_VAL(pCtx, pCtx->size);
-
-    char *pData = GET_INPUT_CHAR(pCtx);
-    if (pCtx->order == TSDB_ORDER_ASC) {
-      memcpy(pCtx->aOutputBuf, pData, (size_t) pCtx->size * pCtx->inputBytes);
-    } else {
-      for(int32_t i = 0; i < pCtx->size; ++i) {
-        memcpy(pCtx->aOutputBuf + (pCtx->size - 1 - i) * pCtx->inputBytes, pData + i * pCtx->inputBytes,
-               pCtx->inputBytes);
-      }
+    for(int32_t i = 0; i < pCtx->size; ++i) {
+      memcpy(pCtx->aOutputBuf + (pCtx->size - 1 - i) * pCtx->inputBytes, pData + i * pCtx->inputBytes,
+             pCtx->inputBytes);
     }
   }
 
@@ -2931,20 +2924,18 @@ static void col_project_function(SQLFunctionCtx *pCtx) {
 
 static void col_project_function_f(SQLFunctionCtx *pCtx, int32_t index) {
   SResultInfo *pResInfo = GET_RES_INFO(pCtx);
-  
+  if (pCtx->numOfParams == 2) {  // the number of output rows should not affect the final number of rows, so set it to be 0
+    return;
+  }
+
   // only one output
   if (pCtx->param[0].i64Key == 1 && pResInfo->numOfRes >= 1) {
     return;
   }
 
-  if (pCtx->numOfParams == 2) {  // the number of output rows should not affect the final number of rows, so set it to be 0
-    SET_VAL(pCtx, pCtx->size, 1);
-    tVariantDump(&pCtx->param[1], pCtx->aOutputBuf, pCtx->outputType, true);
-  } else {
-    INC_INIT_VAL(pCtx, 1);
-    char *pData = GET_INPUT_CHAR_INDEX(pCtx, index);
-    memcpy(pCtx->aOutputBuf, pData, pCtx->inputBytes);
-  }
+  INC_INIT_VAL(pCtx, 1);
+  char *pData = GET_INPUT_CHAR_INDEX(pCtx, index);
+  memcpy(pCtx->aOutputBuf, pData, pCtx->inputBytes);
 
   pCtx->aOutputBuf += pCtx->inputBytes;
 }