qq794554587的博客

配置日志;数据库表的主键ID 分布式系统唯一ID生产：雪花算法；@TableID自动更新update_time乐观锁,干什么都不去上锁 version表字段 并发时 不能更改版本，悲观锁，干什么都上锁逻辑删除，从数据库中没有删除，通过变量让他失效deleted=0=>1增加字段添加@主键，添加配置@Bean性能分析插件：分析每条sql的执行时间 在测试环境用条件构造器： Wraper 条件查询也就是代码自动生成器...

JDBC开发步骤：注册驱动：Class.forName(“com.mysql.jdbc.Driver”);连接数据库：String URL="jdbc:mysql://localhost:3306/数据库名?useUnicode=true&characterEncoding=utf8";String username="root";String password="123456"Connection conn=DriverManager.getConnection(URL,usern

1140 In aggregated query without GROUP BY, expression #1 of SELECT list contains nonaggregated column ‘football.order.id’; this is incompatible with sql_mode=only_full_group_bymysql5.7执行sql语句报错：In aggregated query without GROUP BY, expression #1 of SELECT

# 基本查询SELECT id,zname,zno,zbirthday,zgender,zweight,zheight,zage FROM `t_soldiers`;SELECT id,zname,zage*2 FROM t_soldiers;SELECT id,zname,zage+12 FROM t_soldiers;SELECT id,zname,zage-2 FROM t_soldiers;SELECT id,zname,zage/2 FROM t_soldiers;SELECT i.

//1.注册安装驱动 Class.forName("com.mysql.jdbc.Driver"); String url="jdbc:mysql://localhost:3306/myemployees"; String user="root"; String passworld="123456"; //2.连接数据库 Connection con = DriverManager.getCon...