Oracle 优化效率

一、链接：

ORACLE多表查询优化

oracle的 分表 详解 -----表分区

Oracle数据库查询优化方案（处理上百万级记录如何提高处理查询速度）

数据库SQL优化大总结之 百万级数据库优化方案

解决模糊查询速度慢问题(ORACLE)

二、首先最重要的是要看懂Oracle执行计划分析SQL

https://www.cnblogs.com/Dreamer-1/p/6076440.html

1、rownum

(1)

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

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 = ''
                 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 = ''
)
select yg.* from qybm , yg where qybm.qybm = yg.qyghdm
)

3、索引