Fix empty select exprs for the view created from from item.

src/sql/rewrite/ob_transform_utils.cpp

@@ -7292,6 +7292,11 @@ int ObTransformUtils::create_view_with_from_items(ObDMLStmt* stmt, ObTransformer
     LOG_WARN("failed to get column exprs", K(ret));
   } else if (OB_FAIL(add_new_table_item(ctx, stmt, view, view_table))) {
     LOG_WARN("failed to add table items", K(ret));
+  } else if (OB_ISNULL(view_table->ref_query_)) {
+    LOG_WARN("get unexpected ref query", K(ret));
+  } else if (select_exprs.empty() &&
+             OB_FAIL(ObTransformUtils::create_dummy_select_item(*view_table->ref_query_, ctx))) {
+    LOG_WARN("failed to create dummy select item", K(ret));           
   } else if (OB_FAIL(create_columns_for_view(ctx, *view_table, stmt, select_exprs, column_exprs))) {
     LOG_WARN("failed to create column items", K(ret));
   } else if (OB_FAIL(view->adjust_subquery_list())) {

unittest/sql/rewrite/result/test_transformer_stmt_after_together.result

@@ -38178,6 +38178,54 @@ SQL: select t1.c1 from t1, (select c2 from t1 where 1 = any(select t3.c2 from t3
         }
       ],
       "select": [
+         {
+          "expression": {
+            "item_type":"T_INT",
+            "result_type": {
+              "meta": {
+                "type":"BIGINT",
+                "collation":"binary",
+                "coercibility":"NUMERIC"
+              },
+              "accuracy": {
+                "length":-1,
+                "precision":-1,
+                "scale":-1
+              },
+              "flag":1,
+              "calc_type": {
+                "type":"NULL",
+                "collation":"invalid_type",
+                "coercibility":"INVALID"
+              }
+            },
+            "expr_info": [
+              "IS_CONST",
+              "CNT_CONST"
+            ],
+            "rel_id": [
+            ],
+            "value": {
+              "BIGINT":1
+            }
+          },
+          "is_alias":false,
+          "alias_name":"1",
+          "expr_name":"1",
+          "default": {
+            "NULL":"NULL"
+          },
+          "paramed_alias_name":"",
+          "questions_pos": [
+          ],
+          "params_idx": [
+          ],
+          "esc_str_flag":false,
+          "need_check_dup_name":false,
+          "implicit_filled":false,
+          "is_unpivot_mocked_column":false,
+          "is_hidden_rowid":false
+        }
       ],
       "distinct":false,
       "rollup":false,