Oracle查询窗口功能

Question

请假设我有一个名为MYDATA Oracle表，有如下内容：

NAME, D1,   D2 
A,  01/01/2010, 02/03/2010 
B,  03/03/2010, 20/03/2010 
C,  10/03/2010, 20/09/2010 
D,  10/12/2010, 31/12/2010 


Insert into MYDATA 
    (NAME, D1, D2) 
Values 
    ('A', TO_DATE('01/01/2010 00:00:00', 'MM/DD/YYYY HH24:MI:SS'), TO_DATE('03/02/2010 00:00:00', 'MM/DD/YYYY HH24:MI:SS')); 
Insert into MYDATA 
    (NAME, D1, D2) 
Values 
    ('B', TO_DATE('03/03/2010 00:00:00', 'MM/DD/YYYY HH24:MI:SS'), TO_DATE('03/20/2010 00:00:00', 'MM/DD/YYYY HH24:MI:SS')); 
Insert into MYDATA 
    (NAME, D1, D2) 
Values 
    ('C', TO_DATE('03/10/2010 00:00:00', 'MM/DD/YYYY HH24:MI:SS'), TO_DATE('09/20/2010 00:00:00', 'MM/DD/YYYY HH24:MI:SS')); 
Insert into MYDATA 
    (NAME, D1, D2) 
Values 
    ('D', TO_DATE('12/10/2010 00:00:00', 'MM/DD/YYYY HH24:MI:SS'), TO_DATE('12/31/2010 00:00:00', 'MM/DD/YYYY HH24:MI:SS')); 
COMMIT; 

我想与标记“S”具有重叠的时间间隔记录：在这种情况下，记录B和记录C重叠。

我写了下面的Oracle查询：

SELECT name, D1, D2, WMSYS.WM_CONCAT (OVERLAPPING) 
    FROM (SELECT T1.name, T1.D1, T1.D2, NULL OVERLAPPING 
       FROM MYDATA T1, MYDATA T2 
      WHERE NOT ((T1.D1, T1.D2) OVERLAPS (T2.D1, T2.D2)) 
        AND T1.NAME <> T2.NAME 
      UNION 
      SELECT T1.name, T1.D1, T1.D2, 'S' 
       FROM MYDATA T1, MYDATA T2 
      WHERE ((T1.D1, T1.D2) OVERLAPS (T2.D1, T2.D2)) 
        AND T1.NAME <> T2.NAME) 
GROUP BY NAME, D1, D2; 

结果是：

NAME, D1,   D2,   WMSYS.WM_CONCAT(OVERLAPPING) 
A, 01/01/2010, 02/03/2010, NULL 
B, 03/03/2010, 20/03/2010, S 
C, 10/03/2010, 20/09/2010, S 
D, 10/12/2010, 31/12/2010, NULL 

正如你所看到的，MYDATA加入本身的表 'S' 重叠的记录标记。 我知道，当一个表连接时，相应的查询可以使用Oracle窗口函数重写。

最后，使用Oracle窗口函数重写查询如下：

SELECT NAME, 
      D1, 
      D2 
    FROM (SELECT T1.NAME, 
        T1.D1, 
        T1.D2 
       FROM MYDATA T1, MYDATA T2 
      WHERE ((T1.D1, T1.D2) OVERLAPS (T2.D1, T2.D2)) 
        AND T1.NAME <> T2.NAME) 
GROUP BY NAME, D1, D2; 

你能我请帮忙重写查询，避免了自加入？

非常感谢您考虑我的要求。

Answer 1

您可以使用case与lead和lag：

SELECT D.*, 
     CASE 
      WHEN LAG (D1) OVER (ORDER BY D1) IS NOT NULL 
       AND (LAG (D1) OVER (ORDER BY D1), LAG (D2) OVER (ORDER BY D1)) 
         OVERLAPS (D1, D2) 
       OR LEAD (D1) OVER (ORDER BY D1) IS NOT NULL 
        AND (LEAD (D1) OVER (ORDER BY D1), 
         LEAD (D2) OVER (ORDER BY D1)) 
         OVERLAPS (D1, D2) 
      THEN 
       'S' 
      ELSE 
       'N' 
     END 
      OVERLAP 
    FROM MYDATA D; 

结果：

NAME            D1  D2  OVERLAP 
-------------------------------------------------- --------- --------- ------- 
A             01-JAN-10 02-MAR-10 N  
B             03-MAR-10 20-MAR-10 S  
C             10-MAR-10 20-SEP-10 S  
D             10-DEC-10 31-DEC-10 N