排序导致性能较慢
优化策略：1.尽量不使用排序 2.只查有索引的结果然后 内连接查询
select bizchance0_.* from biz_chance bizchance0_, biz_bizcustomer bizbizcust1_
where bizchance0_.uuid=bizbizcust1_.recordinfoid and bizchance0_.ispublic=1 order by bizchance0_.orderkey desc limit 0,10;
时间 33秒 order by 排序性能较慢 原因：select bizchance0_.* 如果只查select bizchance0_.uuid uuid带索引 性能提高
select bizchance0_.uuid as uid from biz_chance bizchance0_, biz_bizcustomer bizbizcust1_
where bizchance0_.uuid=bizbizcust1_.recordinfoid and bizchance0_.ispublic=1 order by bizchance0_.orderkey desc limit 0,10 ;
时间 3秒
select * from biz_chance as uu inner join (select bizchance0_.uuid as uid from biz_chance bizchance0_, biz_bizcustomer bizbizcust1_
where bizchance0_.uuid=bizbizcust1_.recordinfoid and bizchance0_.ispublic=1 order by bizchance0_.orderkey desc limit 0,10 ) as u on u.uid=uu.uuid
inner join biz_bizcustomer as cus on uu.uuid=cus.recordinfoid
综合 语句
2.筛选条件、顺序不对
select * from biz_customer as cus
left join biz_config400 as conf on conf.customerid=cus.uuid
left join biz_billinginfo as bill on bill.configid=conf.uuid and bill.customerid=cus.uuid
用时 15秒
原因：“and bill.customerid=cus.uuid ”
优化结果
select cus.* from biz_customer as cus
left join biz_config400 as conf on conf.customerid=cus.uuid
left join biz_billinginfo as bill on bill.configid=conf.uuid
where bill.customerid=cus.uuid or bill.uuid is null
或者
select cus.* from biz_customer as cus
left join biz_config400 as conf on conf.customerid=cus.uuid
left join biz_billinginfo as bill on bill.configid=conf.uuid