modify value is null in nchar compare

src/client/src/tscSQLParser.c

@@ -6852,6 +6852,7 @@ int32_t validateOrderbyNode(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, SSqlNode* pSq
   const char* msg5 = "only primary timestamp/column in top/bottom function allowed as order column";
   const char* msg6 = "only primary timestamp allowed as the second order column";
   const char* msg7 = "only primary timestamp/column in groupby clause allowed as order column";
+  const char* msg8 = "only column in groupby clause allowed as order column";
   const char* msg10 = "not support distinct mixed with order by";
   const char* msg11 = "not support order with udf";
   const char* msg12 = "order by tags not supported with diff/derivative/csum/mavg/stateCount/stateDuration";
@@ -7064,7 +7065,16 @@ int32_t validateOrderbyNode(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, SSqlNode* pSq
       if (!validOrder) {
         return invalidOperationMsg(pMsgBuf, msg7);
       }
+      pQueryInfo->groupbyExpr.orderType = pItem->sortOrder;
     }else if (isTopBottomUniqueQuery(pQueryInfo)) {
+      SArray *columnInfo = pQueryInfo->groupbyExpr.columnInfo;
+      if (columnInfo != NULL && taosArrayGetSize(columnInfo) > 0) {
+        SColIndex* pColIndex = taosArrayGet(columnInfo, 0);
+
+        if (pColIndex->colIndex != index.columnIndex) {
+          return invalidOperationMsg(pMsgBuf, msg8);
+        }
+      } else {
         int32_t pos = tscExprTopBottomIndex(pQueryInfo);
         assert(pos > 0);
         SExprInfo* pExpr = tscExprGet(pQueryInfo, pos - 1);
@@ -7075,6 +7085,7 @@ int32_t validateOrderbyNode(SSqlCmd* pCmd, SQueryInfo* pQueryInfo, SSqlNode* pSq
         if (pExpr->base.colInfo.colIndex != index.columnIndex && index.columnIndex != PRIMARYKEY_TIMESTAMP_COL_INDEX) {
           return invalidOperationMsg(pMsgBuf, msg5);
         }
+      }
       pQueryInfo->order.order = pItem->sortOrder;
       pQueryInfo->order.orderColId = pSchema[index.columnIndex].colId;
     }else{