关于oralce大批量查询语句速度慢,IO占用高的问题
今天项目中遇到一条sql语句,其中t_userdownreslog表数据4千万条,t_userinfo 数据2千万条.

修改前

select t.user_account username,              t.mobile usermobile,              t.user_id userid,              u.down_type downtype,              u.resourceid appid,                         u.resourcename appname,              u.package_id jarid                from t_userdownreslog u,t_userinfo t        where u.transaction_id = '10111902201098785862'          and t.user_id = u.user_id           and u.down_status=2           and u.tran_type=2;

select /*+FIRST_ROWS*/              t.user_account username,               t.mobile usermobile,              t.user_id userid,              u.down_type downtype,              u.resourceid appid,                         u.resourcename appname,              u.package_id jarid          from t_userdownreslog u,t_userinfo t        where u.transaction_id = '10111902201098785862'          and t.user_id = u.user_id           and u.down_status=2            and u.tran_type=2;