From d8e20daf0394969a389170f1e5e8ad24bc3785f7 Mon Sep 17 00:00:00 2001
From: Haojun Liao <hjliao@taosdata.com>
Date: Thu, 7 Jan 2021 22:38:38 +0800
Subject: [PATCH] [TD-2610]<fix>: null data return nothing in case of stddev
 query.

---
 src/query/src/qAggMain.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/query/src/qAggMain.c b/src/query/src/qAggMain.c
index 9fccb0d627..0754483449 100644
--- a/src/query/src/qAggMain.c
+++ b/src/query/src/qAggMain.c
@@ -1328,7 +1328,7 @@ static void stddev_function_f(SQLFunctionCtx *pCtx, int32_t index) {
   /* the first stage is to calculate average value */
   if (pStd->stage == 0) {
     avg_function_f(pCtx, index);
-  } else {
+  } else if (pStd->num > 0) {
     double avg = pStd->avg;
     void * pData = GET_INPUT_DATA(pCtx, index);
     
-- 
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