cursor_sharing

今天 在 版本 11.1.0.7 的oracle 数据库中运行一条sql 

select count(*) from mread.t_cmp_type_chapter a where 1 = 1and exists (select * from mread.t_cmp_type_bookitem where status = 13 and objectid = a.ebookid)and ebookid in (select bookid from mread.con_bookextrainformation where chargemode = '2')and feestatus = 2and status in (13, 17);

查看 执行计划，发现常量都被变量代替了，网上找到一个相关的参数（cursor_sharing ），关于参数的解析详见：

http://www.cnblogs.com/Richardzhu/archive/2013/01/21/2869837.html