Question

我尝试了许多oracle分析函数来实现我的需求但却无法实现。这是一个简单的例子：

WITH W1 AS (
SELECT 100 key1, 0 key2, 0 key3, 'open'  status, 'date1' date_column FROM DUAL UNION ALL
SELECT 100 key1, 0 key2, 1 key3, 'open'  status, 'date2' date_column FROM DUAL UNION ALL
SELECT 100 key1, 0 key2, 2 key3, 'close' status, 'date3' date_column FROM DUAL UNION ALL
SELECT 100 key1, 0 key2, 3 key3, 'close' status, 'date4' date_column FROM DUAL UNION ALL
SELECT 100 key1, 0 key2, 4 key3, 'close' status, 'date5' date_column FROM DUAL UNION ALL
SELECT 100 key1, 0 key2, 5 key3, 'open'  status, 'date6' date_column FROM DUAL UNION ALL
SELECT 100 key1, 0 key2, 6 key3, 'open'  status, 'date7' date_column FROM DUAL )
SELECT W1.*, 
       CASE WHEN LAG(status,1) OVER(PARTITION BY key1,key2 ORDER BY key3) <> status THEN date_column
            ELSE FIRST_VALUE(date_column) OVER (PARTITION BY key1,key2,status ORDER BY key3 RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING ) END as DESIRED
  FROM W1
 ORDER BY 1,2,3

我正在尝试在状态更改时获得有序组的第一个值。我只需要在DESIRED列上的最后一行应该是＆＃34; date6＆＃34;

你有什么建议吗？ Oracle 11gr2

感谢。

Answer 1

从Oracle 12c R1（12.1）开始，有一个行限制条款

你可以只使用FETCH FIRST 1 ROWS;

   WITH W1 AS (
    SELECT 100 key1, 0 key2, 0 key3, 'open'  status, 'date1' date_column FROM DUAL UNION ALL
    SELECT 100 key1, 0 key2, 1 key3, 'open'  status, 'date2' date_column FROM DUAL UNION ALL
    SELECT 100 key1, 0 key2, 2 key3, 'close' status, 'date3' date_column FROM DUAL UNION ALL
    SELECT 100 key1, 0 key2, 3 key3, 'close' status, 'date4' date_column FROM DUAL UNION ALL
    SELECT 100 key1, 0 key2, 4 key3, 'close' status, 'date5' date_column FROM DUAL UNION ALL
    SELECT 100 key1, 0 key2, 5 key3, 'open'  status, 'date6' date_column FROM DUAL UNION ALL
    SELECT 100 key1, 0 key2, 6 key3, 'open'  status, 'date7' date_column FROM DUAL )
    SELECT W1.*, 
           CASE WHEN LAG(status,1) OVER(PARTITION BY key1,key2 ORDER BY key3) <> status THEN date_column
                ELSE FIRST_VALUE(date_column) OVER (PARTITION BY key1,key2,status ORDER BY key3 RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING ) END as DESIRED
      FROM W1
     ORDER BY 1,2,3
     FETCH FIRST 1 ROWS ONLY;

请参阅文档https://oracle-base.com/articles/12c/row-limiting-clause-for-top-n-queries-12cr1

Oracle比有序组

1 个答案: