mysql视图(view),临时表与内存表

参考资料:MySql视图view的使用：创建、修改、删除

视图

• 概念:view是基于sql语句结果集的可视化表，是有查询结果形成的一张虚拟表

• 作用:试图刻意隐藏一些敏感字段和数据，查询更加简单高效。

• Mysql创建视图
  create view view_name as select 查询语句
  先有两张表article articleCategory
  
  CREATE VIEW v_article AS SELECT A.title, A.content, A.author, C.name AS categoryName FROM article AS A JOIN articleCategory AS C ON A.articleCategoryId=C.articleCategoryId;

• Myql修改视图
  ALTER VIEW 视图名 AS SELECT 查询语句;

  ALTER VIEW v_article AS SELECT A.title, A.content, A.author, C.name AS categoryName, A.createdOn FROM article AS A JOIN articleCategory AS C ON A.articleCategoryId=C.articleCategoryId WHERE A.published=true;

• 删除视图
  drop view view_name

临时表

• 建表语句
  create temporary table tmp_name as select 查询语句
  select * from tmp_name
  drop temporary table tmp_name
  临时表只存在当前连接中,断开连接就自动drop

内存表

create table mem_table() engine=memory 建表语句
engine=memory

总结

视图可以永久保存，临时表只存在当前连接，内存表重启表结构保存，数据丢失