Every derived table must have its own alias详解数据库

如下SQL语句：

SELECT * FROM  
( SELECT ID,URL FROM alone_action  WHERE STATE = '1' ) 

在Oracle中可以执行，但在MySQL下无法通过，错误如下:

查询：SELECT * FROM ( SELECT ID,URL FROM alone_action WHERE STATE = '1' ) LIMIT 0, 1000 
 
错误代码： 1248 
Every derived table must have its own alias

Every derived table must have its own alias 意思是说 每个派生出来的表都必须有一个自己的别名 , 因为进行嵌套查询的时候子查询出来的的结果是作为一个派生表来进行上一级的查询的，所以子查询的结果必须要有一个别名

把MySQL语句改为如下即可

SELECT * FROM  
( SELECT ID,URL FROM alone_action  WHERE STATE = '1' ) as t

        -------------------- 分割线 -------------------- 

作者出现上述错误的原因不是单纯执行SQL的问题，而是有个项目是Oracle的需要迁移到MySQL，数据库迁移成功之后 运行报错

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Every derived table must have its own alias

原因是因为Hibernate的dialect方言问题，将配置文件中Oracle的方言改为MySQL即可

<property name="dialect"> 
    org.hibernate.dialect.MySQLDialect 
</property>

附：RDBMS 方言