关于oracle调优
场景1:查询时间过长
select u.*,t.*
(select sum(l.all_pl2)
from TABLE_A l
where 1 = 1
and l.tx_dt <= '20201223'
and u.investor_id = l.investor_id) as sum_all_pl2
from TABLE_C u
inner join (select t2.*
from (select t.*
rank() over(partition by investor_id order by tx_dt desc) rowno
from TABLE_B t
where t.tx_dt <= '20201223') t2
where 1 = 1
and t2.rowno = 1) t3 on u.investor_id = t3.investor_id
where 1 = 1
order by HEX(CONVERT( a.create_date USING GBK ))
select count(1) from TABLE_A;--结果集1104207
select count(1)from TABLE_B;--结果集7257
1.查看表是否有索引，为关联字段添加索引
create index idx_tablieatxdtinvid on TABLE_A (INVESTOR_ID, TX_DT);
create index idx_tablieatxdt on TABLE_A (TX_DT);
create index idx_tablieainvid on TABLE_A (INVESTOR_ID);2.表字段的索引主要针对数值型的varchar2或者number有效。
3.排序字段最好使用数值的varchar2或者number。尽量不使用非数字排序（yyyy-dd-mm，uuid，中英文等）
4.关联字段的类型最好统一，尽量不要用varchar2和number关联（varchar2的数值和number字段关联，减少oracle的隐式转换）
5.主键可以使用封装的@getNextSequence方法获取
