diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index b0ea89f7c4a2e007f8ad06a8e042d665f42ee66c..25ac16ce58ec110d1162723499617704fe6ad350 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -996,9 +996,16 @@ int32_t tscValidateSqlInfo(SSqlObj* pSql, struct SSqlInfo* pInfo) {
         return code;
       }
 
-      // set the command/global limit parameters from the first subclause to the sqlcmd object
-      pCmd->active = pCmd->pQueryInfo;
-      pCmd->command = pCmd->pQueryInfo->command;
+      // set the command/global limit parameters from the first not empty subclause to the sqlcmd object
+      SQueryInfo* queryInfo = pCmd->pQueryInfo;
+      int16_t command = queryInfo->command;
+      while (command == TSDB_SQL_RETRIEVE_EMPTY_RESULT && queryInfo->sibling != NULL) {
+        queryInfo = queryInfo->sibling;
+        command = queryInfo->command;
+      }
+
+      pCmd->active = queryInfo;
+      pCmd->command = command;
 
       STableMetaInfo* pTableMetaInfo1 = tscGetMetaInfo(pCmd->active, 0);
       if (pTableMetaInfo1->pTableMeta != NULL) {
diff --git a/tests/develop-test/2-query/4-union/union-order.py b/tests/develop-test/2-query/4-union/union-order.py
new file mode 100644
index 0000000000000000000000000000000000000000..6c2f20c129d294601f89757d01710f5e080a1717
--- /dev/null
+++ b/tests/develop-test/2-query/4-union/union-order.py
@@ -0,0 +1,60 @@
+###################################################################
+#           Copyright (c) 2021 by TAOS Technologies, Inc.
+#                     All rights reserved.
+#
+#  This file is proprietary and confidential to TAOS Technologies.
+#  No part of this file may be reproduced, stored, transmitted,
+#  disclosed or used in any form or by any means other than as
+#  expressly provided by the written permission from Jianhui Tao
+#
+###################################################################
+
+# -*- coding: utf-8 -*-
+
+import sys
+from util.log import *
+from util.cases import *
+from util.sql import *
+
+
+class TDTestCase:
+    def caseDescription(self):
+        '''
+        case1<shenglian zhou>: [TD-12229]fix union all query produces different result when switch query
+        ''' 
+        return
+    
+    def init(self, conn, logSql):
+        tdLog.debug("start to execute %s" % __file__)
+        tdSql.init(conn.cursor(), logSql)
+        self._conn = conn
+
+    def run(self):
+        print("running {}".format(__file__))
+        tdSql.execute("drop database if exists td12229")
+        tdSql.execute("create database if not exists td12229")
+        tdSql.execute('use td12229')
+
+        tdSql.execute('create stable st(ts timestamp , value int ) tags (ind int)') 
+        tdSql.execute('insert into tb1 using st tags(1) values(now ,1)') 
+        tdSql.execute('insert into tb1 using st tags(1) values(now+1s ,2)') 
+        tdSql.execute('insert into tb1 using st tags(1) values(now+2s ,3)') 
+        tdSql.execute('create stable ste(ts timestamp , value int ) tags (ind int)') 
+        tdSql.query('select * from st')
+        tdSql.checkRows(3)
+        tdSql.query('select * from st union all select * from ste')
+        tdSql.checkRows(3)
+        tdSql.query('select * from ste union all select * from st')
+        tdSql.checkRows(3)
+        tdSql.query('select elapsed(ts) from ste group by tbname union all select elapsed(ts) from st group by tbname;')
+        tdSql.checkRows(1)
+        tdSql.query('select elapsed(ts) from st group by tbname union all select elapsed(ts) from ste group by tbname;')
+        tdSql.checkRows(1)
+        tdSql.execute('drop database td12229')
+    def stop(self):
+        tdSql.close()
+        tdLog.success("%s successfully executed" % __file__)
+
+
+tdCases.addWindows(__file__, TDTestCase())
+tdCases.addLinux(__file__, TDTestCase())
diff --git a/tests/develop-test/fulltest.sh b/tests/develop-test/fulltest.sh
index e7f272fc073a66685bdca709cc6434bb9838b5aa..016c75e03eb62430d6e48a5ebb775e05dc1a26d0 100755
--- a/tests/develop-test/fulltest.sh
+++ b/tests/develop-test/fulltest.sh
@@ -1,3 +1,4 @@
 python3 test.py -f 0-management/3-tag/json_tag.py
 python3 test.py -f 1-insert/0-sql/batchInsert.py
+python3 test.py -f 2-query/4-union/union-order.py
 python3 test.py -f 2-query/7-nest/ts_hidden_column.py