sql - 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？

Question

我正在 Responsys 中执行此查询并解释计划。

此查询的解释计划运行良好，并返回大约 70 行计数数据：

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

WHERE ROWNUM <= 10但在末尾添加行限制子句：

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

解释计划中的这个错误导致：

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）：解释计划将 statement_id ='ACME_CUST:1550184818627' 放入 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 <= 10

我正在寻找的结果只是 LOCATION 的前 10 行计数。

Answer 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 <= 10

其他形式见这篇文章：如何正确使用Oracle ORDER BY 和ROWNUM？