[TS-1254]<fix>: fix keepColumnName with signle column

src/client/src/tscSQLParser.c

@@ -2593,14 +2593,14 @@ static int32_t setExprInfoForFunctions(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, SS
 void setResultColName(char* name, tSqlExprItem* pItem, int32_t functionId, SStrToken* pToken, bool multiCols) {
   if (pItem->aliasName != NULL) {
     tstrncpy(name, pItem->aliasName, TSDB_COL_NAME_LEN);
-  } else if (multiCols) {
+  } else {
     char uname[TSDB_COL_NAME_LEN] = {0};
     int32_t len = MIN(pToken->n + 1, TSDB_COL_NAME_LEN);
     tstrncpy(uname, pToken->z, len);
 
     if (tsKeepOriginalColumnName) { // keep the original column name
       tstrncpy(name, uname, TSDB_COL_NAME_LEN);
-    } else {
+    } else if (multiCols) {
       if (!TSDB_FUNC_IS_SCALAR(functionId)) {
         int32_t size = TSDB_COL_NAME_LEN + tListLen(aAggs[functionId].name) + 2 + 1;
         char    tmp[TSDB_COL_NAME_LEN + tListLen(aAggs[functionId].name) + 2 + 1] = {0};
@@ -2615,10 +2615,10 @@ void setResultColName(char* name, tSqlExprItem* pItem, int32_t functionId, SStrT
 
         tstrncpy(name, tmp, TSDB_COL_NAME_LEN);
       }
+    } else  { // use the user-input result column name
+      len = MIN(pItem->pNode->exprToken.n + 1, TSDB_COL_NAME_LEN);
+      tstrncpy(name, pItem->pNode->exprToken.z, len);
     }
-  } else  { // use the user-input result column name
-    int32_t len = MIN(pItem->pNode->exprToken.n + 1, TSDB_COL_NAME_LEN);
-    tstrncpy(name, pItem->pNode->exprToken.z, len);
   }
 }