什么是延遲索引？使用索引查詢出來數據，之后把查詢結果和同一張表中數據進行連接查詢，進而提高查詢速度!

分頁是一個很常見功能，select ** from tableName limit ($page - 1 ) * $n ,$n

通過一個存儲過程插入10000條數據進行測試：

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()

begin

declare num int default 100001;

while num < 1000000 do

set num := num +1;

insert into smth1 values (num ,num,'我是*****','我是誰');

end while ;

end;

查詢：

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 |

可見隨著查詢$page 變大，時間會越來越大！

怎樣避免這種情況？

一般我們數據庫里面數據都不會直接刪除，數據時很寶貴的，不舍得刪除，另一方便能提高查詢數據

先利用索引查詢出來數據，再進行聯合查詢不就行了

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 ;

進行執行計劃分析，沒有一個大于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，還會想到用in來查詢而不是子查詢，為什么不用in，使用in會先查詢出來一條id，之后再去和下面進行匹配，會進行smth1進行全表掃描！

相關標簽：索引

本文原創發布php中文網，轉載請注明出處，感謝您的尊重！

總結

以上是生活随笔為你收集整理的mysql延时优化教程_Mysql优化之延迟索引和分页优化_MySQL的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。