我有一个查询,旨在向我显示表 A 中最近尚未更新的任何行。 (每行应在“month_no”之后的 2 个月内更新。):
SELECT A.identifier
, A.name
, TO_NUMBER(DECODE( A.month_no
, 1, 200803
, 2, 200804
, 3, 200805
, 4, 200806
, 5, 200807
, 6, 200808
, 7, 200809
, 8, 200810
, 9, 200811
, 10, 200812
, 11, 200701
, 12, 200702
, NULL)) as MONTH_NO
, TO_NUMBER(TO_CHAR(B.last_update_date, 'YYYYMM')) as UPD_DATE
FROM table_a A
, table_b B
WHERE A.identifier = B.identifier
AND MONTH_NO > UPD_DATE
WHERE 子句中的最后一行导致“ORA-00904 无效标识符”错误。不用说,我不想在 WHERE 子句中重复整个 DECODE 函数。有什么想法吗? (修复和解决方法均已接受...)
最佳答案
这不可能直接实现,因为按时间顺序,WHERE 发生在 SELECT 之前,这始终是执行链中的最后一步。
您可以对其进行子选择和过滤:
SELECT * FROM
(
SELECT A.identifier
, A.name
, TO_NUMBER(DECODE( A.month_no
, 1, 200803
, 2, 200804
, 3, 200805
, 4, 200806
, 5, 200807
, 6, 200808
, 7, 200809
, 8, 200810
, 9, 200811
, 10, 200812
, 11, 200701
, 12, 200702
, NULL)) as MONTH_NO
, TO_NUMBER(TO_CHAR(B.last_update_date, 'YYYYMM')) as UPD_DATE
FROM table_a A
, table_b B
WHERE A.identifier = B.identifier
) AS inner_table
WHERE
MONTH_NO > UPD_DATE
从评论中移出一些有趣的信息:
There should be no performance hit. Oracle does not need to materialize inner queries before applying outer conditions -- Oracle will consider transforming this query internally and push the predicate down into the inner query and will do so if it is cost effective. – Justin Cave
关于sql - 在 WHERE 子句中使用别名,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/356675/