使用match_recognize时收到错误ORA-00918

Question

我正在尝试学习Oracle 12c引入的模式匹配。 但是从下面的代码中模糊地定义了ORA-00918：列。 不知道我在哪里错过

    SELECT CUSTOMER_ID,ORDER_TOTAL,ORDER_TIMESTAMP FROM DEMO_ORDERS MATCH_RECOGNIZE(
  PARTITION BY CUSTOMER_ID
  ORDER BY CUSTOMER_ID,ORDER_TIMESTAMP

  MEASURES
   A.CUSTOMER_ID AS CUSTOMER,
    A.ORDER_TOTAL AS TOTAL_AMT,
    A.ORDER_TIMESTAMP AS WHEN_HPA
   ALL ROWS PER MATCH
  PATTERN( A B* )
  DEFINE
    B AS (B.ORDER_TOTAL < PREV(B.ORDER_TOTAL))


    )

Answer 1

问题是您的order by子句； 似乎同时看到了原始表列的customer_id和匹配分区值。

但是，您正在按customer_id分区，因此按顺序进行排序毫无意义。 该排序适用于分区内（如分析功能中一样）。 因此，您可以删除它：

SELECT CUSTOMER_ID,ORDER_TOTAL,ORDER_TIMESTAMP FROM DEMO_ORDERS MATCH_RECOGNIZE(
  PARTITION BY CUSTOMER_ID
  ORDER BY ORDER_TIMESTAMP
...