使用 ROW_NUMBER() 窗口函数而不指定 ORDER BY

Question

我在 Oracle 18c 中有一个

polygons

表和一个

points

表。

CREATE TABLE polygons (objectid NUMBER(4,0), shape SDO_GEOMETRY);
INSERT INTO polygons  (objectid,shape) 
       VALUES (1,SDO_GEOMETRY(2003, 26917, NULL, sdo_elem_info_array(1, 1003, 1), 
       sdo_ordinate_array(668754.6396, 4869279.7913, 668782.1453, 4869276.1585, 668790.9678, 4869344.6631, 668762.4242, 4869346.22, 668754.6396, 4869279.7913)));

CREATE TABLE points (objectid NUMBER(4,0), shape SDO_GEOMETRY);
INSERT INTO  points (objectid,shape) VALUES (1,SDO_GEOMETRY(2001, 26917, sdo_point_type(668768.133,  4869255.3995, NULL), NULL, NULL));
INSERT INTO  points (objectid,shape) VALUES (2,SDO_GEOMETRY(2001, 26917, sdo_point_type(668770.2088, 4869306.259,  NULL), NULL, NULL));
INSERT INTO  points (objectid,shape) VALUES (3,SDO_GEOMETRY(2001, 26917, sdo_point_type(668817.9545, 4869315.0815, NULL), NULL, NULL));
INSERT INTO  points (objectid,shape) VALUES (4,SDO_GEOMETRY(2001, 26917, sdo_point_type(668782.1134, 4869327.1634, NULL), NULL, NULL));

我有一个查询选择在空间上至少相交一点的多边形。

  SELECT poly_objectid
    FROM (SELECT poly.objectid as poly_objectid,
                 row_number() over(partition by poly.objectid order by null) rn
            FROM polygons poly
      CROSS JOIN points pnt
           WHERE sdo_anyinteract(poly.shape, pnt.shape) = 'TRUE'
         )
   WHERE rn = 1

   POLY_OBJECTID 
   ------------- 
               1

-------------------------------------------------------------------------------------
| Id  | Operation                | Name     | Rows  | Bytes | Cost (%CPU)| Time     |
-------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT         |          |     1 |    26 |    20  (70)| 00:00:01 |
|*  1 |  VIEW                    |          |     1 |    26 |    20  (70)| 00:00:01 |
|*  2 |   WINDOW SORT PUSHED RANK|          |     1 |  7671 |    20  (70)| 00:00:01 |
|   3 |    NESTED LOOPS          |          |     1 |  7671 |    19  (69)| 00:00:01 |
|   4 |     TABLE ACCESS FULL    | POLYGONS |     1 |  3848 |     3   (0)| 00:00:01 |
|*  5 |     TABLE ACCESS FULL    | POINTS   |     1 |  3823 |    16  (82)| 00:00:01 |
-------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - filter("RN"=1)
   2 - filter(ROW_NUMBER() OVER ( PARTITION BY "POLY"."OBJECTID" ORDER BY NULL )<=1)
   5 - filter("MDSYS"."SDO_ANYINTERACT"("POLY"."SHAPE","PNT"."SHAPE")='TRUE')
 
Note
-----
   - dynamic statistics used: dynamic sampling (level=2)

db<>小提琴

查询仅使用

row_number()

和

WHERE rn = 1

每个多边形选择一行。这按预期工作。

---

问题：

当多边形与多个点相交时，选择哪一行对我来说并不重要。保留任何多边形行都可以。

换句话说，

order by null desc

中的

row_number()

是不必要的。

出于简单性和性能原因，是否有一种方法可以从分析/窗口函数中省略

order by null desc

？

---

相关：

使用 SQL 空间关系函数时处理“仅第一个实例”

Answer 1

如果您不需要某些特定列的顺序，您可以简单地使用 rownum。 rownum 只是 Oracle 查找结果行的顺序，没有任何特定规则。