<fix>[TD-11459]It is empty if stddev with group by nchar

src/client/src/tscSubquery.c

@@ -2272,7 +2272,15 @@ void tscFirstRoundRetrieveCallback(void* param, TAOS_RES* tres, int numOfRows) {
             if (row[i] == NULL) {
               setNull(p + offset, pExpr->base.resType, pExpr->base.resBytes);
             } else {
-              memcpy(p + offset, row[i], length[i]);
+              if(pExpr->base.resType == TSDB_DATA_TYPE_NCHAR){
+                int32_t output = 0;
+                bool ret = taosMbsToUcs4(row[i], length[i], p + offset, pExpr->base.resBytes, &output);
+                if (!ret) {
+                  tscError("stddev convert tag error:%d", ret);
+                }
+              }else{
+                memcpy(p + offset, row[i], length[i]);
+              }
             }
             offset += pExpr->base.resBytes;
           }

tests/pytest/functions/function_stddev.py

@@ -123,8 +123,34 @@ class TDTestCase:
         tdSql.execute("insert into t1 values(now, 1, 'abc');")
         tdLog.info("select stddev(k) from t1  where b <> 'abc' interval(1s);")
         tdSql.query("select stddev(k) from t1  where b <> 'abc' interval(1s);")
-        
-            
+
+        #add for TD-11459
+        tdSql.execute("create table stdtable(ts timestamp, col1 int) tags(loc nchar(64))")
+        tdSql.execute("create table std1 using stdtable tags('beijing')")
+        tdSql.execute("create table std2 using stdtable tags('shanghai')")
+        tdSql.execute("create table std3 using stdtable tags('河南')")
+        tdSql.execute("insert into std1 values(now + 1s, 1)")
+        tdSql.execute("insert into std1 values(now + 2s, 2);")
+        tdSql.execute("insert into std2 values(now + 3s, 1);")
+        tdSql.execute("insert into std2 values(now + 4s, 2);")
+        tdSql.execute("insert into std3 values(now + 5s, 4);")
+        tdSql.execute("insert into std3 values(now + 6s, 8);")
+        tdSql.query("select stddev(col1) from stdtable group by loc;")
+        tdSql.checkData(0, 0, 2.0)
+        tdSql.checkData(1, 0, 0.5)
+        tdSql.checkData(2, 0, 0.5)
+
+        tdSql.execute("create table stdtableint(ts timestamp, col1 int) tags(num int)")
+        tdSql.execute("create table stdint1 using stdtableint tags(1)")
+        tdSql.execute("create table stdint2 using stdtableint tags(2)")
+        tdSql.execute("insert into stdint1 values(now + 1s, 1)")
+        tdSql.execute("insert into stdint1 values(now + 2s, 2);")
+        tdSql.execute("insert into stdint2 values(now + 3s, 1);")
+        tdSql.execute("insert into stdint2 values(now + 4s, 2);")
+        tdSql.query("select stddev(col1) from stdtableint group by num")
+        tdSql.checkData(0, 0, 0.5)
+        tdSql.checkData(1, 0, 0.5)
+
     def stop(self):
         tdSql.close()
         tdLog.success("%s successfully executed" % __file__)