+1°
要求：获得按 table1_id 分组，并且取得 table2 中 age 最大的记录信息。
方法一：
select * from (select * from table2 order by age desc) as a group by a.table1_id
方法二：
select a.* from table2 as a where age = (select max(age) from table2 where a.table1_id=table1_id)
方法三：
select a.* from table2 as a where not exists (select * from table2 where table1_id=a.table1_id and age>a.age)
方法四：
...
MySQL, 分组, 最大值阅读全文
+1°
1. 配置 spring-security 时报错为：Configuration problem: Unable to locate Spring NamespaceHandler for XML schem
原因：忘记添加 spring-security.config.jar 文件
2. ERROR [ContextLoader] Context initialization failed org.springframework.beans.factory.parsing.BeanDefinitionParsingException: Configuration problem: Unable to locate Spring NamespaceHandler for XML schema namespace [http://www.springfr...
Error, Spring, 框架, 配置阅读全文
