diff --git a/src/sql/optimizer/ob_del_upd_log_plan.cpp b/src/sql/optimizer/ob_del_upd_log_plan.cpp
index 30cba06912..8e19af2014 100644
--- a/src/sql/optimizer/ob_del_upd_log_plan.cpp
+++ b/src/sql/optimizer/ob_del_upd_log_plan.cpp
@@ -263,11 +263,12 @@ int ObDelUpdLogPlan::check_table_rowkey_distinct(
       } else if (OB_FAIL(index_dml_info->get_rowkey_exprs(rowkey_exprs))) {
         LOG_WARN("failed to get rowkey exprs", K(ret));
       } else if (OB_FAIL(ObOptimizerUtil::is_exprs_unique(rowkey_exprs,
+                                                          best_plan->get_table_set(),
                                                           best_plan->get_fd_item_set(),
                                                           best_plan->get_output_equal_sets(),
                                                           best_plan->get_output_const_exprs(),
                                                           is_unique))) {
-          LOG_WARN("check dml is order unique failed", K(ret));
+        LOG_WARN("check dml is order unique failed", K(ret));
       } else if (!is_unique) {
         index_dml_info->distinct_algo_ = T_HASH_DISTINCT;
       } else {
diff --git a/src/sql/resolver/ddl/ob_create_table_resolver.cpp b/src/sql/resolver/ddl/ob_create_table_resolver.cpp
index 50ea3b06af..e665b2069e 100644
--- a/src/sql/resolver/ddl/ob_create_table_resolver.cpp
+++ b/src/sql/resolver/ddl/ob_create_table_resolver.cpp
@@ -1695,6 +1695,7 @@ int ObCreateTableResolver::resolve_table_elements_from_select(const ParseNode &p
 {
   int ret = OB_SUCCESS;
   ObCreateTableStmt *create_table_stmt = static_cast<ObCreateTableStmt *>(stmt_);
+  const ObTableSchema *base_table_schema = NULL;
   ParseNode *sub_sel_node = parse_tree.children_[CREATE_TABLE_AS_SEL_NUM_CHILD - 1];
   ObSelectStmt *select_stmt = NULL;
   ObSelectResolver select_resolver(params_);
@@ -1806,7 +1807,9 @@ int ObCreateTableResolver::resolve_table_elements_from_select(const ParseNode &p
       }
       for (int64_t i = 0; OB_SUCC(ret) && i < select_items.count(); ++i) {
         const SelectItem &select_item = select_items.at(i);
-        const ObRawExpr *expr = select_item.expr_;
+        ObRawExpr *expr = select_item.expr_;
+        ObColumnRefRawExpr *new_col_ref = static_cast<ObColumnRefRawExpr *>(expr);
+        TableItem *new_table_item = select_stmt->get_table_item_by_id(new_col_ref->get_table_id());
         if (OB_UNLIKELY(NULL == expr)) {
           ret = OB_ERR_UNEXPECTED;
           LOG_WARN("select item expr is null", K(ret), K(i));
@@ -1817,6 +1820,25 @@ int ObCreateTableResolver::resolve_table_elements_from_select(const ParseNode &p
           } else {
             column.set_column_name(select_item.expr_name_);
           }
+          if (OB_SUCC(ret) && is_mysql_mode() &&
+              new_table_item != NULL &&
+              new_table_item->is_basic_table()) {
+            if (base_table_schema == NULL &&
+                OB_FAIL(schema_checker_->get_table_schema(session_info_->get_effective_tenant_id(),
+                                                          new_table_item->ref_id_, base_table_schema))) {
+              LOG_WARN("get table schema failed", K(ret));
+            } else if (OB_ISNULL(base_table_schema)) {
+              ret = OB_ERR_UNEXPECTED;
+              LOG_WARN("NULL table schema", K(ret));
+            } else {
+             const ObColumnSchemaV2 *org_column = base_table_schema->get_column_schema(select_item.expr_name_);
+             if (NULL != org_column &&
+                !org_column->is_generated_column() &&
+                !org_column->get_cur_default_value().is_null()) {
+                column.set_cur_default_value(org_column->get_cur_default_value());
+              }
+            }
+          }
           if (ObResolverUtils::is_restore_user(*session_info_)
               && ObCharset::case_insensitive_equal(column.get_column_name_str(), OB_HIDDEN_PK_INCREMENT_COLUMN_NAME)) {
             continue;
diff --git a/src/sql/rewrite/ob_transform_simplify_groupby.cpp b/src/sql/rewrite/ob_transform_simplify_groupby.cpp
index ffcc1dab06..fc3b132184 100644
--- a/src/sql/rewrite/ob_transform_simplify_groupby.cpp
+++ b/src/sql/rewrite/ob_transform_simplify_groupby.cpp
@@ -629,9 +629,15 @@ int ObTransformSimplifyGroupby::remove_group_by_duplicates(ObDMLStmt *&stmt, boo
       }
     }
     if (OB_SUCC(ret)) {
-      select_stmt->get_group_exprs().reset();
-      if (OB_FAIL(select_stmt->get_group_exprs().assign(new_group_exprs))) {
-        LOG_WARN("failed to assign a new group exprs", K(ret));
+      if (new_group_exprs.count() == group_exprs.count()) {
+        //do nothing
+      } else {
+        select_stmt->get_group_exprs().reset();
+        if (OB_FAIL(select_stmt->get_group_exprs().assign(new_group_exprs))) {
+          LOG_WARN("failed to assign a new group exprs", K(ret));
+        } else {
+          trans_happened = true;
+        }
       }
     }
   }