#ACID

mysql中innodb和myisam对比及索引原理区别-云栖社区-阿里云

Published at April 29, 2019 ·  1 min read

如何选择 mysql 中的索引。 innoDB 支持事物和外键,支持 4 个事务隔离级别,回滚,崩溃修复能力和多版本并发的事务安全,包括 ACID,如果应用中需要执行大量的 insert 或 update 操作,则应该使用 InnoDB,这样可以提高多用户并发操作的性能,MyISAM 管理非事务表,提供高速存储和检索,以及全文搜索能力。如果应用中需要大量的 select 查询,则选择 MyISAM。InnoDB 使用的聚簇索引、索引就是数据,顺序存储,因此能缓存索引,也能缓存数据。MyISAM 堆组织表 使用的是非聚簇索引、索引和文件分开,随即存储,只能缓存索引。MyISAM 读写互相阻塞:不仅会在写入的时候阻塞读取,MyISAM 还会在读取的时候阻塞写入,但读本身并不会阻塞另外的读。InnoDB 读写阻塞与事务隔离级别相关。 mysql中innodb和myisam对比及索引原理区别-云栖社区-阿里云...


SQL vs NoSQL Database Differences Explained with few Example DB

Published at April 11, 2019 ·  1 min read

非常详细的解释了 sql 和 nosql 之间的区别。1. sql 是基于 table 的,而 nosql 是基于 document,kv 对,图或者 宽表,也就是说在 sql 中,sql 是包含若干 table,而 nosql 则是若干 document 的集合。2. 复杂的查询,我想这也是两者最为关键的区别,sql 可以轻易的完成多种条件关系组合的复杂查询,而 nosql 却将这种复杂的关系固化到 document 的 kv 组合中 3. 两者在 scale 时的区别sql 适合 vertically scalable,也就是说,提高服务器的硬件,比如 ram,cpu,disk 之类即可提高数据库的负载性能,而 nosql 则是需要通过增加数据库服务器的数量来提高负载。4. sql 设计遵循 acid, atomicity, consistency, isolation, durability, nosql 则遵循 cap , consistency, availability and partition tolerance SQL vs NoSQL Database Differences Explained with few Example DB...


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