MySQL中,MyISAM中索引文件和数据文件分开存储,均为 非聚焦索引,主索引 额外要求了主键的唯一性;InnoDB的数据按照 存储在 聚焦索引 B+Tree的叶子节点中,其余索引中叶子节点保存的值为 聚焦索引主键的值,所以 其他索引 一般需要查询两次 B+Tree才可获取数据(例外的情况是 覆盖索引,建立多个列的组合索引,而搜索的值...
解决:在SqlMapConfig.xml中配置数据链接池,使用连接池管理数据库链接。 ● Sql语句写在代码中造成代码不易维护,实际应用sql变化的可能较大,sql变动需要改变java代码。解决:将Sql语句配置在XXXXmapper.xml文件中与java代码分离。 ●向sql语句传参数麻烦,因为sql语句的where条件不一定,可能多也可能少,占位符需要和参数一...
java_interview_questions 随笔分类 -java_interview_questions java后端开发面试题 面试题 摘要:题目: 以下程序的输出结果是: 选项: A:9 B:18 C:20 D:21 E:22阅读全文 posted @2019-10-07 22:03helloworldmybokeyuan阅读(121)评论(0)推荐(0) 2019春招面试题总结-06...
假设在配置文件中编写了一条insert语句,那么这条语句需要的值从哪里来呢,在mybatis的mapper配置中有parameterType属性,该属性是专门给sql语句占位符传值的,其实这里也是使用了反射机制,其中sql语句的占位符采用#{},其中大括号当中需要提供java对象的属性名,该属性名和get进行拼接得到get方法名,然后通过反射机制获取该get...
java api中对问题中所用String构造方法的解释: public String(String original) Initializes a newly created String object so that it represents the same sequence of characters as the argument; in other words, the newly created string is a copy of the argument string. Unless an explicit copy of or...
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Tutorial and How to Guide on various topics related to Java Programming Language - Core Java, Spring, Webservices, REST, Hibernate, Maven and Microservices.
Popular JavaScript / React / Node / Mongo stack Interview questions and their answers. Many of them, I faced in actual interviews and ultimately got my first full-stack Dev job :) - GitHub - rohan-paul/Awesome-JavaScript-Interviews: Popular JavaScript /
JDBC Interview Questions Answers part-1 By Ranjeet Jha / java / 4 Comments what questions will ask in java interview about JDBC interview questions? JDBC (Java Database Connectivity) is used to connect database to perform database operations: create, read, update, delete....
MyBatis和MyBatis-Plus都是针对Java持久层框架MyBatis的增强工具,它们之间有以下几个主要区别: 使用方式: MyBatis是一个优秀的持久层框架,它提供了基于XML或注解的SQL映射配置,开发者需要手动编写SQL语句和映射配置。 MyBatis-Plus是在MyBatis的基础上进行增强,提供了更多的便捷功能和增强特性,使用MyBatis-Plus可以...