为什么将工作查询限制为 WHERE ROWNUM <=10 会导致 EXPLAIN PLAN “ORA-12899: value too large for column”出错？答案

【问题标题】：Why does limiting a working query by WHERE ROWNUM <=10 result in an error from the EXPLAIN PLAN "ORA-12899: value too large for column"?为什么将工作查询限制为 WHERE ROWNUM <=10 会导致 EXPLAIN PLAN “ORA-12899: value too large for column”出错？
【发布时间】：2019-07-09 20:34:52
【问题描述】：

我正在 Responsys 中执行此查询并解释计划。

这个查询的解释计划运行良好，返回大约 70 行计数数据：

select * from ( Select LOCATION, count(LOCATION) COUNT_LOCATION From TABLE Group By LOCATION Order By COUNT_LOCATION Desc )

但在末尾添加行限制WHERE ROWNUM <= 10子句：

select * from ( Select LOCATION, count(LOCATION) COUNT_LOCATION From TABLE Group By LOCATION Order By COUNT_LOCATION Desc ) WHERE ROWNUM <= 10

解释计划结果中的这个错误：

错误：java.sql.SQLException：ORA-00604：递归 SQL 级别 1 发生错误 ORA-12899：列“ACME_CUST”的值太大。“PLAN_TABLE”。“OPTIONS”（实际：33，最大值：30 ) : 将计划集 statement_id ='ACME_CUST:1550184818627' 解释为 acme_CUST.PLAN_TABLE for select * from (Select LOCATION, count(LOCATION) COUNT_LOCATION From TABLE Group By LOCATION Order By COUNT_LOCATION Desc ) WHERE ROWNUM

我正在寻找的结果只是 LOCATION 的前 10 行数。

【问题讨论】：

该错误表明不是您的查询导致错误，而是尝试对该查询执行 EXPLAIN PLAN。您是否明确执行 EXPLAIN PLAN？如果没有，您使用的任何客户端工具似乎都在隐含地这样做，并且可能导致错误。
我正在使用电子邮件服务平台 Responsys，它代表我执行 EXPLAIN PLAN。我会将它们作为标签添加到这个问题中。

标签： sql oracle11g responsys

【解决方案1】：

尝试在排序上使用 ROW_NUMBER()。我认为这是因为 GROUP BY/ORDER BY 组合与 ROWNUM 结合使用：

select * from ( Select LOCATION, count(LOCATION), COUNT_LOCATION, ROW_NUMBER() OVER (ORDER BY COUNT_LOCATION GROUP BY LOCATION Desc) RowNumbers From TABLE Group By LOCATION Order By COUNT_LOCATION Desc) WHERE RowNumbers

其他形式见本文：How to use Oracle ORDER BY and ROWNUM correctly?

【讨论】：