優(yōu)化Limit查詢
優(yōu)化步驟1:使用有索引的列或主鍵進(jìn)行ORDER BY操作
SELECT film_id,description from sakia.film ORDER BY film_id limit 50.5
優(yōu)化步驟2:記錄上次返回的主鍵,在下次查詢時(shí)使用主鍵過濾
SELECT film_id,description FROM sakila.film WHERE film_id >55 and film_id<=60 ORDERY BY film_id Limit 1,5
優(yōu)化步驟1:使用有索引的列或主鍵進(jìn)行ORDER BY操作
SELECT film_id,description from sakia.film ORDER BY film_id limit 50.5
優(yōu)化步驟2:記錄上次返回的主鍵,在下次查詢時(shí)使用主鍵過濾
SELECT film_id,description FROM sakila.film WHERE film_id >55 and film_id<=60 ORDERY BY film_id Limit 1,5
2015-04-13
離散程度的大小的判定方法:
計(jì)算出數(shù)據(jù)庫中記錄不重復(fù)數(shù)量
select count(distinct row1),count(distinct row2) from table;
count()值大的就離散度高。
計(jì)算出數(shù)據(jù)庫中記錄不重復(fù)數(shù)量
select count(distinct row1),count(distinct row2) from table;
count()值大的就離散度高。
2015-04-13
select count(release_year),release_year from film where release_year between 2006 and 2007 group by release_year
2015-04-09
老師講得很好,涉及了MySQL優(yōu)化相關(guān)的很多方面,從總結(jié)到細(xì)分,['SQL&索引','庫表結(jié)構(gòu)','軟件配置',‘硬件配置’],能夠幫助大家快速地對MySQL的優(yōu)化建立初始體系,不過畢竟時(shí)間有限,希望后續(xù)能有機(jī)會(huì)聽到老師在SQL、索引和庫表結(jié)構(gòu)方面更多的分享。
再次感謝:)
再次感謝:)
2015-04-03