一、链接：

 

 

二、首先最重要的是要看懂Oracle执行计划分析SQL

 

1、rownum

(1)

SELECT ywlsdm, qybm, spzt, czsj, czrydm FROM GH_hs WHERE ywlsdm in (SELECT ywlsdm FROM GH_hs WHERE spzt = '2')

2、with as 临时表

select * from (with qybm as (select gx.qybm          from (select a.ghdm                   from gh_ghdm a                  start with a.ghdm = '1'                 connect by prior a.ghdm = a.sjghdm) gh         inner join gh_qyghgx gx on gh.ghdm = gx.tjghdm         ),yg as (   select * from gh_jc_yg t where t.yglx = '0')select yg.* from qybm , yg where qybm.qybm = yg.qyghdm )

 3、索引