ThreePerson博客

## mysql 两表关联批量更新 ``` update table1,table2 set table1.column1 = table2.column2 where table1.column2 = table2.column3 ``` 解释： 表一和表二通过table

## springboot 指定配置环境启动 业务环境：本地修复线上数据，需要连接线上地址 配置文件配置： ``` 1.application-release.properties 配置线上外网访问地址 2.application.properties 添加配置：sprin

## 业务需求:数据不存在则插入，存在则更新 更新时需要判断某个字段是否为null 为null时更新 ``` <insert id="insertOrupdate" parameterType="java.util.List"> insert into tbl_gold_res

## mysql表tbl_gold_resource 字段phone, job_number添加唯一键 删除重复数据 sql如下： ``` DELETE FROM tbl_gold_resource WHERE id IN ( select * from (

## Java 8中将集合List转变为用逗号分隔的String 1.String.join() 此方法适用于List<String> ``` List<String> list= Arrays.asList("aaa", "bbb", "ccc", "ddd"); String s

String s1 = "false"; String s2 = "true"; String s3 = "fAlSe"; String s4 = "TrUe"; String s5 = "true_a";

## list对象的转换 对象Staff ``` public class Staff { private String name; private int age; private BigDecimal salary; } ```

啊

## 如何用grep 查询中所匹配模式的最后一项 grep "aa" file | tail -n 1

## Mysql 中将blob类型转换成varchar类型 ``` select CAST(blobfield AS CHAR(10000) CHARACTER SET utf8) from table ```