diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index dca70d0cbbd141223c921c9fe0258ef7c37fa62d..8ac47d1ec3b6278256568ec3d57998dd1fb0bdd1 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -4598,7 +4598,7 @@ static void setDefaultOrderInfo(SQueryInfo* pQueryInfo) {
 int32_t parseOrderbyClause(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, SQuerySQL* pQuerySql, SSchema* pSchema) {
   const char* msg0 = "only support order by primary timestamp";
   const char* msg1 = "invalid column name";
-  const char* msg2 = "only support order by primary timestamp or queried column";
+  const char* msg2 = "only support order by primary timestamp or first tag in groupby clause allowed";
   const char* msg3 = "invalid column in order by clause, only primary timestamp or first tag in groupby clause allowed";
 
   setDefaultOrderInfo(pQueryInfo);
diff --git a/src/query/src/qAggMain.c b/src/query/src/qAggMain.c
index 9fccb0d627fc4574ef90865e94e43c10cbdfc9bf..075448344971b545920b28f8d07198f2babe91c2 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);
     
diff --git a/src/query/src/qHistogram.c b/src/query/src/qHistogram.c
index 0d31948e59e520452605ac4577b695c53b3fad6c..98b825c11f32642bdc1a16e83a76c9686fdecd46 100644
--- a/src/query/src/qHistogram.c
+++ b/src/query/src/qHistogram.c
@@ -143,6 +143,9 @@ SHistogramInfo* tHistogramCreateFrom(void* pBuf, int32_t numOfBins) {
 
   SHistogramInfo* pHisto = (SHistogramInfo*)pBuf;
   pHisto->elems = (SHistBin*)((char*)pBuf + sizeof(SHistogramInfo));
+  for(int32_t i = 0; i < numOfBins; ++i) {
+    pHisto->elems[i].val = -DBL_MAX;
+  }
 
   pHisto->maxEntries = numOfBins;
 
diff --git a/src/query/tests/histogramTest.cpp b/src/query/tests/histogramTest.cpp
index 82fd4bcf9907eeb1286f9b6d0976e541e7b1a16b..3088d6f8078483c39ec3780250e8bfa2d613f218 100644
--- a/src/query/tests/histogramTest.cpp
+++ b/src/query/tests/histogramTest.cpp
@@ -4,42 +4,9 @@
 #include <iostream>
 
 #include "taos.h"
-#include "tsdb.h"
-
-#include "tstoken.h"
-#include "tutil.h"
-
 #include "qHistogram.h"
-
-/* test validate the names for table/database */
-TEST(testCase, histogram_binary_search) {
-  SHistogramInfo* pHisto = tHistogramCreate(MAX_HISTOGRAM_BIN);
-
-  pHisto->numOfEntries = 10;
-  for (int32_t i = 0; i < 10; ++i) {
-    pHisto->elems[i].num = 1;
-    pHisto->elems[i].val = i;
-  }
-
-  int32_t idx = histoBinarySearch(pHisto->elems, pHisto->numOfEntries, 1);
-  assert(idx == 1);
-
-  idx = histoBinarySearch(pHisto->elems, pHisto->numOfEntries, 9);
-  assert(idx == 9);
-
-  idx = histoBinarySearch(pHisto->elems, pHisto->numOfEntries, 20);
-  assert(idx == 10);
-
-  idx = histoBinarySearch(pHisto->elems, pHisto->numOfEntries, -1);
-  assert(idx == 0);
-
-  idx = histoBinarySearch(pHisto->elems, pHisto->numOfEntries, 3.9);
-  assert(idx == 4);
-
-  free(pHisto);
-}
-
-TEST(testCase, histogram_add) {
+namespace {
+void doHistogramAddTest() {
   SHistogramInfo* pHisto = NULL;
 
   /**
@@ -99,6 +66,56 @@ TEST(testCase, histogram_add) {
   tHistogramDestroy(&pRes);
   free(res);
 }
+void doHistogramRepeatTest() {
+  SHistogramInfo* pHisto = NULL;
+  struct timeval systemTime;
+
+  gettimeofday(&systemTime, NULL);
+  int64_t st =
+      (int64_t)systemTime.tv_sec * 1000L + (uint64_t)systemTime.tv_usec / 1000;
+
+  for (int32_t i = 0; i < 1000; ++i) {
+    tHistogramAdd(&pHisto, -24 + i);
+    //        tHistogramPrint(pHisto);
+  }
+
+  tHistogramDestroy(&pHisto);
+
+}
+}
+
+/* test validate the names for table/database */
+TEST(testCase, histogram_binary_search) {
+  SHistogramInfo* pHisto = tHistogramCreate(MAX_HISTOGRAM_BIN);
+
+  pHisto->numOfEntries = 10;
+  for (int32_t i = 0; i < 10; ++i) {
+    pHisto->elems[i].num = 1;
+    pHisto->elems[i].val = i;
+  }
+
+  int32_t idx = histoBinarySearch(pHisto->elems, pHisto->numOfEntries, 1);
+  assert(idx == 1);
+
+  idx = histoBinarySearch(pHisto->elems, pHisto->numOfEntries, 9);
+  assert(idx == 9);
+
+  idx = histoBinarySearch(pHisto->elems, pHisto->numOfEntries, 20);
+  assert(idx == 10);
+
+  idx = histoBinarySearch(pHisto->elems, pHisto->numOfEntries, -1);
+  assert(idx == 0);
+
+  idx = histoBinarySearch(pHisto->elems, pHisto->numOfEntries, 3.9);
+  assert(idx == 4);
+
+  free(pHisto);
+}
+
+TEST(testCase, histogram_add) {
+  doHistogramAddTest();
+  doHistogramRepeatTest();
+}
 
 TEST(testCase, heapsort) {
   //    int32_t num = 20;
diff --git a/tests/script/general/parser/tags_filter.sim b/tests/script/general/parser/tags_filter.sim
index e05776ff11a67fb0b577219046044fdc8e825dc8..d77581582846e98fe4e11a1a717c9336ebb69566 100644
--- a/tests/script/general/parser/tags_filter.sim
+++ b/tests/script/general/parser/tags_filter.sim
@@ -73,6 +73,9 @@ endi
 sql select * from stb where t1 > '1'
 sql select * from stb where t1 > 'a'
 
+print =====================> TD-2685
+sql_error select t1, count(t1) from stb;
+
 ## wildcard '%' 
 #sql select * from stb where t1 like '%'
 #if $rows != 1 then