哪个网站买域名好,wordpress改了固定链接访问不,深圳华强做网站,wordpress表单 慢什么是延迟索引#xff1f;使用索引查询出来数据#xff0c;之后把查询结果和同一张表中数据进行连接查询#xff0c;进而提高查询速度!分页是一个很常见功能#xff0c;select ** from tableName limit ($page - 1 ) * $n ,$n通过一个存储过程插入10000条数据进行测试使用索引查询出来数据之后把查询结果和同一张表中数据进行连接查询进而提高查询速度!分页是一个很常见功能select ** from tableName limit ($page - 1 ) * $n ,$n通过一个存储过程插入10000条数据进行测试create table smth1 (id int auto_increment ,ver int(11) default null,content varchar(1000) not null,intro varchar(1000) not null,primary key(id),key idver(id,ver))engine innodb default charset utf8;create procedure smthTest1()begindeclare num int default 100001;while num 1000000 doset num : num 1;insert into smth1 values (num ,num,我是*****,我是谁);end while ;end;查询mysql show profiles;--------------------------------------------------------------------| Query_ID | Duration | Query |--------------------------------------------------------------------| 1 | 0.002006 | select id ,content from smth1 limit 1000,10 || 2 | 0.030106 | select id ,content from smth1 limit 5000,10 || 3 | 0.042428 | select id ,content from smth1 limit 9000,10 || 4 | 0.01297225 | select id ,content from smth1 limit 10000,10 || 5 | 0.13077625 | select id ,content from smth1 limit 20000,10 |可见随着查询$page 变大时间会越来越大怎样避免这种情况一般我们数据库里面数据都不会直接删除数据时很宝贵的不舍得删除另一方便能提高查询数据先利用索引查询出来数据再进行联合查询不就行了select C.id,C.content from smth1 C inner join(select id from smth1 where id 1000 limit 10) as t on C.id t.id ;select C.id,C.content from smth1 C inner join(select id from smth1 where id 5000 limit 10) as t on C.id t.id ;select C.id,C.content from smth1 C inner join(select id from smth1 where id 9000 limit 10) as t on C.id t.id ;select C.id,C.content from smth1 C inner join(select id from smth1 where id 10000 limit 10) as t on C.id t.id ;select C.id,C.content from smth1 C inner join(select id from smth1 where id 20000 limit 10) as t on C.id t.id ;进行执行计划分析没有一个大于1s的11 | 0.04538625 | select C.id,C.content from smth1 C inner join(select id from smth1 where id 5000 limit 10) as t on C.id t.id || 12 | 0.023278 | select C.id,C.content from smth1 C inner join(select id from smth1 where id 9000 limit 10) as t on C.id t.id || 13 | 0.02320425 | select C.id,C.content from smth1 C inner join(select id from smth1 where id 10000 limit 10) as t on C.id t.id || 14 | 0.001938 | select C.id,C.content from smth1 C inner join(select id from smth1 where id 20000 limit 10) as t on C.id t.id |此外还会想到用in来查询而不是子查询为什么不用in使用in会先查询出来一条id之后再去和下面进行匹配会进行smth1进行全表扫描相关标签索引本文原创发布php中文网转载请注明出处感谢您的尊重
