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HomeDatabaseMysql Tutorial 为什么要用非关系型数据库

1. 数据库事务一致性需求 很多web实时系统并不要求严格的数据库事务,对读一致性的要求很低,有些场合对写一致性要求也不高。因此数据库事务管理成了数据库高负载下一个沉重的负担。 2. 数据库的写实时性和读实时性需求 对关系数据库来说,插入一条数据之后

1. 数据库事务一致性需求

 

很多web实时系统并不要求严格的数据库事务,对读一致性的要求很低,有些场合对写一致性要求也不高。因此数据库事务管理成了数据库高负载下一个沉重的负担。

 

2. 数据库的写实时性和读实时性需求

 

对关系数据库来说,插入一条数据之后立刻查询,是肯定可以读出来这条数据的,但是对于很多web应用来说,并不要求这么高的实时性,比方说我(JavaEye的robbin)发一条消息之后,,过几秒乃至十几秒之后,我的订阅者才看到这条动态是完全可以接受的。

 

3、对复杂的SQL查询,特别是多表关联查询的需求

 

任何大数据量的web系统,都非常忌讳多个大表的关联查询,以及复杂的数据分析类型的复杂SQL报表查询,特别是SNS类型的网站,从需求以及产品设计角度,就避免了这种情况的产生。往往更多的只是单表的主键查询,以及单表的简单条件分页查询,SQL的功能被极大的弱化了。

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